> Introduction

This deck was born while I was looking for Doomsday piles to put into my first Marchesa's deck.
Eventually, I found this article about how to combo off with Doomsday and Grenzo, Dungeon Warden (I'd put the link, but I think the website has been taken down time ago). It was really cool and very well explained, so I started to brew my own version. It came together quite easily and, in a matter of few months, I already had a stable build.
At the beginning, I wanted this to be a semi-casual deck, but with time it became more and more optimized and many "competitive" cards eventually replaced others that were perfoming no that well. After all, you know... It never felt quite right to claim my deck was "semi-casual" and then kill the table with a Doomsday.
Anyway, compared to other established cEDH lists, there are a lot of cards that are still missing. Some (like Badlands, for instance) are just too expensive for me to purchase, others come from more recent sets and, since I virtually stopped playing Magic with the Walking Dead, I tend to take my time before ever consider them.
By the way, the deck is still quite strong. I'd say is a 4 on a rating scale from 1 to 5 (where 1 means "casual" and 5 means "competitive").

> Gameplay

The deck mostly relies on using Grenzo's ability to flip creatures from the bottom of your library. Roughly have 1/3 of the cards are creatures, so the chances of flipping one are quite decent, but you still need some setup in order to reliably have some impact on the game. Moreover, most of them have power 2 or less, so you can cast Grenzo as soon as turn 2 (with X=0) and still get value out of him. You could find way of pumping him later on.
Being a 2-mana commander makes Grenzo quite easy to recast (after a removal etc.). Nonetheless, there is no need to expose him if you're not planning to activate him any time soon. So think about developing your board state first.
The best time to flip a card is generally at the end of the last turn before you get to untap, so that your creatures don't die to sorcery-speed wrath effects. If you have Thran Turbine out you can wait until your upkeep, but flipping after your draw step is a risk because, if you happen to flip Maralen of the Mornsong, all your opponents will get to tutor whatever they want before you.
The main win condition is Doomsday, that allows you to stack the bottom of your library with one of the many combos in the deck.
In theory, you could win as soon as turn 3, provided you cast Grenzo, Dungeon Warden on turn 2 and follow up with Doomsday the next turn, with something like Dark Ritual or Sol Ring that lets you have 2 spare mana open. In some situation, you could even spend turn 1 casting Vampiric Tutor to search for missing combo pieces and still be able to go off at turn 3.
As a downside, not having access to blue, you'll have a hard time protecting Doomsday when you're trying to go off. By the way, the most problematic issue is against stax: cards like Torpor Orb or Cursed Totem can single-handedly shut down your entire strategy.
Moreover, it's worth noting that Grenzo's ability isn't affected by graveyard hate like Rest in Peace. The creature still gets onto the battlefield even if it didn't touch the bin.

> Opening Hand

In general, any opening hand with 2 mana sources is fair game. Better yet if accompanied with some tutoring effect.
As already said, you generally want Grenzo out as soon as possible to start flipping cards, even if the chances to actually hit a creature are initially quite low. Any tool that could help you to improve these odds are also welcome.
Remember that, with the London mulligan rule, you can purposedly go below 7 cards and send to the bottom of your library any relevant creature that you're willing to flip later on.
From this point onward, your main goal is to gather enough resources to go for the combo line that better fits in with the cards you have. Otherwise, you won't tipically play cards from your hand, unless you really need to answer to some threat.

> Combos

The deck runs many combos. In fact, it's not that unusual to accidentally assemble one of them by just randomly flipping cards with Grenzo.
Here's the list:

> Kiki-Jiki, Mirror Breaker + Zealous Conscripts

This is probably the easiest combo to assemble, since it only requires 2 cards and you only need to find a way to pump Grenzo's power by 1 to flip them from the bottom of your library.
The only disadvantage is that you have to pass through your combat phase, so you can't win at instant speed.
For those who don't know the combo, you basically tap Kiki-Jiki to copy Zealous Conscripts. When the token enters the battlefield you target Kiki-Jiki, gaining control (unrelevant) and untapping it. You can now repeat the process as many times as you want, making infinite hasty tokens and attacking everyone for lethal damage.

> Kiki-Jiki, Mirror Breaker + Skirk Prospector/Viscera Seer + Lightning Crafter

This combo requires 3 cards but can win at instant speed, since it relies on direct damage and doesn't need to pass through the combat phase.
Although you can use Viscera Seer too, Skirk Prospector is slightly better because it nets you mana in the process and it's a goblin. This is particularly important because, as you'll get to see in a moment, this deck has several ways to fetch goblins and there are several cards that care about goblins in general.
The combo works as follows: you copy Lightning Crafter with Kiki-Jiki, the token champions Kiki-Jiki, then you tap it to deal 3 damage and sacrifice it. Kiki-Jiki returns to play untapped, so that you can repeat the process as many times you want until you kill everybody.

> Murderous Redcap + Skirk Prospector/Viscera Seer + Metallic Mimic

The upside of this combo is that you don't need to pump Grenzo to flip it, since all creatures have power 2 or less.
Here, you name Goblin with Metallic Mimic, then you sacrifice Murderous Redcap so that it will come back to play because of persist, but the -1/-1 counter will be elided with the +1/+1 counter granted by the Mimic. You can repeat the process infinite times, shooting everybody to death with Redcap's triggered ability.

> Maralen of the Mornsong + Opposition Agent/Stranglehold

This isn't technically a combo, since you're not winning right away, but if it gets unanswered your opponents will be prevented from drawing new cards for the rest of the game.
Also, it could be considered a 1-card combo, since you only need to flip Maralen and she will tutor for the other piece by herself.
If you have both cards in play, on your turn you'll pay 3 life to tutor for whatever, on other players' turn they'll still pay 3 life but can't search for anything.
As I said before, Maralen has to hit the battlefield just before your draw step for this to work.

> Goblin Recruiter + Conspicuous Snoop

TODO

> Doomsday Piles

Here I will detail some notable piles you can stack with Doomsday.
It's important to note that they're meant to be a guideline and not an exhaustive list. In fact, sometimes you could have some combo pieces already on the battlefield (or in your hand), other times you could have more or less mana available for extra protection and so on. You should adapt them to the game situation.
Cards are listed in the order they would be flipped by Grenzo, i.e. the first card will go on the bottom and the last on top of your library.

> Priest of Gix - Kiki-Jiki, Mirror Breaker - Mad Auntie - Zealous Conscripts - <whatever>

This is the basic pile and the cheapest one, since it only requires 4 cards and 2 mana to go off.
You can swap Mad Auntie for Brass Herald and get the same result, provided you name rogue when it enters the battlefield.
Steps to follow:

• pay 2 mana to flip Priest of Gix and net 3 black mana in exchange.
• use 2 of those 3 mana to flip Kiki-Jiki, Mirror Breaker, tap it to copy Priest of Gix and net 3 more black mana (4 total).
• use 2 of that mana to flip Mad Auntie and pump Grenzo, Dungeon Warden.
• now that Grenzo is a 3/3, you can use the last 2 mana to flip Zealous Conscripts and go infinite with Kiki-Jiki.

> Priest of Gix - Kiki-Jiki, Mirror Breaker - Murderous Redcap - Skirk Prospector - Metallic Mimic

This pile still requires only 2 mana to go off.
It starts like the previous one, but uses Kiki-Jiki only to make mana and goes for Murderous Redcap combo instead.
Steps to follow:

• pay 2 mana to flip Priest of Gix and net 3 black mana in exchange.
• use 2 of those 3 mana to flip Kiki-Jiki, Mirror Breaker, tap it to copy Priest of Gix and net 3 more black mana (4 total).
• use 2 of that mana to flip Murderous Redcap, shoot whatever you want for 2 damage.
• use the last 2 mana to flip Skirk Prospector, then sacrifice Kiki-Jiki and the Redcap to net 2 red mana.
• in response to Redcap's persist trigger, use that mana to flip Metallic Mimic.
• Murderous Redcap will return to the battlefield with no counters, so you can go infinite.

> Treasonous Ogre - Clone Shell - Lightning Crafter - Kiki-Jiki, Mirror Breaker - Viscera Seer

Aside form the 2 mana, this pile costs 16 life as well. Which is a lot.
Therefore, I don't recommend it but there could be some scenario where you would need it, so it's good to know it exists.
Steps to follow:

• pay 2 mana to flip Workhorse.
• remove 2 counters from Workhorse to flip Clone Shell, look at the other creatures and imprint Mikaeus, the Unhallowed.
• remove the last 2 counters from Workhorse to flip Triskelion.
• pay 2 more mana to flip Viscera Seer, then sacrifice Clone Shell to get Mikaeus back to play.

> Ransack the Lab - Victimize - Mikaeus, the Unhallowed - Triskelion.

This pile doesn't need Grenzo to go off.
The only requirement is to have 3BB mana open and a creature on the battlefield.
Steps to follow:

• draw Ransack the Lab and cast it, keeping Victimize while dropping Mikaeus, the Unhallowed and Triskelion to the graveyard.
• cast Victimize to reanimate them and win the game.

> Insidious Dreams Piles

Many of the piles for Insidious Dreams are essentially the same for Doomsday, with an additional card to put the rest on the bottom of your library.
Most of the piles require you to draw a card, so the better moment to cast Insidious Dreams is right before starting your turn.
Unfortunately, you won't have slots available for mana acceleration, so the focus here is more on the cards you have to discard to pay for Insidious Dreams' additional cost.

> Howltooth Hollow/Spinerock Knoll/Temple of Malice - Maralen of the Mornsong

This pile only requires 2 cards and 3R mana to go off. Therefore, it's the one I recommend in most cases.

• draw the land and play it.
• put Maralen of the Mornsong on the bottom of your library.
• at the end step before starting your turn, flip Maralen.
• on your draw step, tutor for Stranglehold and cast it to lock the board.

> Howltooth Hollow/Spinerock Knoll - Kiki-Jiki, Mirror Breaker - Mad Auntie - Zealous Conscripts

This is the Insidious Dreams version of the first Doomsday pile.

• draw the hideaway land and play it.
• put Kiki-Jiki, Mirror Breaker, Mad Auntie and Zealous Conscripts on the bottom of your library, hiding away the fourth card.
• flip the cards with Grenzo and win the game (you need 6 mana to do so).

> Temple of Malice - Brass Herald - Kiki-Jiki, Mirror Breaker - Zealous Conscripts

Essentially the previous pile, but with Temple of Malice instead of the hideaway land.

• draw Temple of Malice and play it.
• scry the top card of your library, putting Brass Herald on the bottom.
• flip Brass Herald, naming rogue to pump Grenzo, then put the rest on the bottom of your library.
• flip Kiki-Jiki, Mirror Breaker and Zealous Conscripts, then go infinite.

> Howltooth Hollow/Spinerock Knoll - Murderous Redcap - Skirk Prospector - Metallic Mimic

More of the same, but with Murderous Redcap combo instead.
It costs 1 less mana, because you get to sacrifice the Redcap to Skirk Prospector during the process.

> Howltooth Hollow/Spinerock Knoll - Brass Herald - Goblin Recruiter

This pile only requires 3 cards, although you need 7 mana to pull it off.
The trick here is to use the first pile to fetch a second one (namely, the one with only goblins) and go off from that.

• draw the hideaway land and play it.
• look at the top of your library, putting Brass Herald and Goblin Recruiter on the bottom.
• flip Brass Herald, naming rogue to pump Grenzo.
• in response to Brass Herald's trigger, flip Goblin Recruiter and fetch the second pile:
  Skirk Prospector - Siege-Gang Commander - Kiki-Jiki, Mirror Breaker - Lightning Crafter
  • flip Skirk Prospector (you've paid 6 mana so far), then sacrifice Goblin Recruiter to net 1 red mana.
  • pay 1 more mana (7 so far) to flip Siege-Gang Commander, then sacrifice it together with its tokens to net 4 more mana.
  • use 2 of that mana to flip Kiki-Jiki, Mirror Breaker.
  • use the last 2 mana to flip Lightning Crafter and go infinite.

> Temple of Malice - Clone Shell - Mikaeus, the Unhallowed - Viscera Seer - Triskelion

This pile requires one more card to go off, so I don't recommend it.

• draw Temple of Malice and play it.
• scry the top card of your library, putting Clone Shell on the bottom.
• flip Clone Shell, imprint Mikaeus and put the rest on the bottom.
• flip Viscera Seer, then sacrifice Clone Shell to get Mikaeus back to play.
• flip Triskelion and go infinite.

> Temple of Malice - Clone Shell - Lightning Crafter - Viscera Seer - Kiki-Jiki, Mirror Breaker

Same as before, but with Kiki-Jiki instead of Mike & Trike.

> Ransack the Lab - Victimize - Mikaeus, the Unhallowed - Triskelion.

This is exactly the same pile as for Doomsday.
As already pointed out, it requires 3BB mana and a creature on the battlefield, but doesn't need Grenzo to go off.

> Card Analysis

Here goes a description of each card I run in this deck and why.
They can be divided in three categories:

• Staples
  These cards definitely belong to the deck. It's not only my opinion, there is a general consensus over them being good with Grenzo.
  As a rule of thumb, putting them into any Grenzo deck you could be willing to build is a good idea. In fact, not doing so is likely to make your deck worse.
  I'd keep all these cards if I'm going to build a full-competitive decklist.
• Personal Choices
  These cards are good with Grenzo, but it's only my opinion.
  They could be considered as hidden gems, since not that many players run them but, more often than not, it's just that I like them in my deck.
  I'd say most of these cards belong to the casual side of this list, so I'd swap them for more power and interaction if I want to go competitive.
• Competitive Slots
  As the time passed and the list got more optimized, it naturally drifted towards the competitive side.
  These are all inclusions that bring more power to the deck, without being blatantly overpriced.
  I won't recommend them for a more casual metagame, since they're likely to perform poorly.
• Flexible Slots
  These are either recent additions or kind of situational slots.
  I didn't get to test them enough to be sure they belong to the deck, so feel free to replace them with whatever you like more.
  I've been working on this list for some years though, so they aren't that many.

Since most of the cards belong to this category, they shall be considered as staples unless otherwise specified.

> Lands

The deck runs 34 lands, which for my standards is kind of on the lower end of the spectrum.
More competitive builds can probably go even lower, but I prefer to play safe on that.
As the time passes and this list gets further refined though, it's still possible I would shave more lands from it.

• Basic Lands
  Being two-colors, this deck naturally runs a decent amount of basics.
  If you're going to fetch, go for a basic Swamp whenever possible. You could accidentally flip Magus of the Moon at any time and lose access to black, if you don't get prepared.
• Dual Lands
  Here are all the duals that could realistically come into play untapped.
  Some are obvious choices, others are more of a hidden gem like Shadowblood Ridge. In fact, I think Odyssey filter-lands are overall underrated.
• Temple of Malice
  This is an exception to my enter-untapped rule, but one worth it.
  Being able to scry a card to the bottom of your library is invaluable in this deck.
• Bloodstained Mire and Prismatic Vista
  Even if I'm aware that off-color fetchlands are legal, I don't like to put them in my decks (my Gitrog Deck being the only exception so far). Of course, feel free to add them if you so please.
  As already mentioned, go for a basic Swamp whenever possible.
• Any-Color Lands
  These are all obvious inclusions, even if they deal damage when tapped (like City of Brass) they're still to be preferred over any dual tap-lands.
• Path of Ancestry
  Another exception to my enter-untapped rule.
  Again, you can scry a card to the bottom. Totally worth it.
• Cavern of Souls (competitive slot)
  You name goblin, Grenzo and half of your combo pieces are uncounterable. You play this card.
• Ancient Tomb and Crystal Vein
  Sol lands (i.e. lands that give you 2 mana) are especially good here, since they give you the exact amount of mana needed to activate Grenzo.
  City of Traitors could be an obvious upgrade to Crystal Vein, but it's far too expensive for my taste. The latter still being able to achieve its goal.
• Spinerock Knoll and Howltooth Hollow
  Like scry-lands, hideaway lands are invaluable.
  You'll always hideaway the most useless card and stack the others on the bottom, ready to be flipped with Grenzo.
  You could sometime be able to cast the card underneath Spinerock Knoll, but with Howltooth Hollow that's virtually impossible. Not that you really care...
• Urborg, Tomb of Yawgmoth
  You could think you're giving away free access to black to all your opponents. True.
  But this land on turn 3 can mark the difference between casting Doomsday to win the match, and miserably fall into oblivion.
• Volrath's Stronghold (personal choice)
  This card tends to become relevant later in the game, when this deck is likely to lose anyway.
  I won't probably put it in a more competitive build, but it's still a decent inclusion and one of my favourite lands.
  That's enough for me.
• Phyrexian Tower
  A land that can potentially give you 2 mana is always useful, especially if that mana is black.
  Moreover, it's not that unusual to actually be interested in sending one of your creatures to the bin.
• Gemstone Caverns (competitive slot)
  If you get lucky it's essentially a turn-1 Chrome Mox, a card that I'd definitely be glad to see in my starting hand.
  Otherwise, you get a colorless land. Not that exciting, but still useful for activating Grenzo's ability, which isn't that bad after all.

> Ramp

Historically, black/red is a color combination that doesn't have access to a lot of ramp.
In addition, bear in mind that your commander enters on turn 2. So any ramp spell that costs 3 or more mana will make you tap out the next turn for no real benefit, since even if you get to activate Grenzo one more time on turn 4, you're only getting even with the activation you missed on turn 3.

• Chrome Mox (competitive slot)
  In general, I don't use much this kind of spells in EDH because, even if they're very mana-efficient, they put you down a card.
  Card advantage is very important, especially in multiplayer. In a table with 3 opponents, one card less for you means three cards more for them, which is huge.
  At the end of the day though, you don't care about card advantage when you're going to win on the spot.
  Chrome Mox is especially good here, since it's one of the few cards that effectively lets you play Grenzo one turn earlier (other viable options are Mox Diamond and Lotus Petal, which you should consider if you want to turn on the competitive side).
• Sol Ring
  I still have to find a deck where Sol Ring doesn't belong.
• Thran Turbine
  With Grenzo out, it's essentially a free activation each turn. Virtually a second Sol Ring. Yes please.
• Arcane Signet
  If you're not in green, here's your second auto-inclusion after Sol Ring.
• Talisman of Indulgence and Rakdos Signet
  Any two-color deck (and I'd say even three-color) that isn't in green should run all Talismans and Signets in its color identity.
• Dark Ritual
  Same rationale as Chrome Mox.
  By the way, this gives you exactly the mana you need to cast Doomsday. Just saying...

> Goblins

The deck has a small goblin subtheme.
It isn't for flavour reasons though, but just because many combo pieces happen to be gobins as well.

• Skirk Prospector
  A free sac outlet that gives you mana in exchange.
  Mainly a combo piece, you may want to play it even when you're not going off to net some mana.
• Torch Courier
  This card is here only to give Conspicuous Snoop haste. Outside of it, it's pretty useless.
• Goblin Recruiter
  Its main purpose is to stack some Snoop line, although you may sometimes want to go for the classic Kiki-Jiki, Mirror Breaker + Skirk Prospector + Lightning Crafter combo.
  When needed, it can also act as a worse Goblin Matron to fetch utilities that you're willing to cast the next turn.
• Dockside Extortionist (competitive slot)
  Everyone is playing this guy in competitive: it makes a lot of treasure tokens for such a small investment.
  At a more casual table though, you may not see that many artifacts. If so, feel free to swap it for something more in line with your meta.
• Conspicuous Snoop
  This little critter has been a huge update for this deck. It makes Goblin Recruiter essentially a one-card combo.
• Goblin Matron
  Half of your combo pieces are goblins. This tutors for any goblin. You play this.
  Actually, more often than not you'll rather search for some utilities, like Tuktuk Scrapper to remove problematic stax pieces or Mad Auntie to pump and protect your Grenzo. Either ways, you'll always be happy to see it in your hand.
• Tuktuk Scrapper
  When it comes to artifact removal, red offers many options. I've chosen Tuktuk Scrapper because:
  1. it's a creature with power 2, so it can flipped with Grenzo.
  2. it's an enter-the-battlefield ability, so no summoning sickness nor extra mana involved.
  3. it's a goblin, so it can be fetched by many other cards in the deck.
  4. it costs 4 mana, so it can be transmuted into by Fleshwrither.
• Lightning Crafter
  This guy has been quite obsoletized by Conspicuous Snoop. I've decided to keep it in the deck to maximize its combo potential.
  Moreover, it's still a decent pinger and its champion ability can sometime set up some interesting interaction.
• Kiki-Jiki, Mirror Breaker
  Arguably the most valuable card in the deck, for he's a fundamental piece in many combo lines.
  Given his high casting cost, you almost never want to see him in your hand. In fact, you'd find a way to cheat it into play instead.
• Mad Auntie
  She pumps Grenzo so that he can flip creatures with power 3 as well.
  There are many goblin lords out there: Goblin King, Goblin Chieftain... More competitive lists tend to opt for Mogg Raider and/or Goblin Sledder.
  I prefer the Auntie because she has a more relevant body and her regeneration ability can seldom be helpful to protect my general.
• Sling-Gang Lieutenant
  This slot used to be occupied by Siege-Gang Commander.
  The fact that the Lieutenant can be used with Conspicuous Snoop forced me to do the swap.
• Murderous Redcap
  A combo piece that can sometimes act as a removal.
  The fact that it has persist brings even more value to the table.

> Other Creatures

The deck runs as many cretures as possible to keep Grenzo relevant even when there is no combo available.

• Imperial Recruiter
  Like Goblin Matron, but better. Yeah, you play this as well.
• Viashino Heretic
  This is in the list because of Torpor Orb.
  That card alone shuts down all your combos, makes most of your creatures useless, in short: it turns your deck into garbage.
  People tend to use Goblin Cratermaker instead, but with Torpor Orb in play you won't be able to fetch it with Goblin Matron anyway.
• Magus of the Moon
  People not always expect this kind of stax plays from a combo deck.
  If flipped with Grenzo, it will catch many players unprepared, you included. So again, fetch for a basic Swamp whenever possible.
• Treasonous Ogre (competitive slot)
  One mana for three life isn't as cheap as you might expect. Activating Grenzo twice will already cost you 12 life, so I won't go wild with this.
  Nonetheless, it's more than enough to flip a Doomsday pile for free. Actually, quite broken.
• Moggcatcher
  People often overlook this card, but by resolving this critter you're basically putting a clock of 2 turns on the game.
  If you get to activate it, you can fetch Goblin Recruiter and win with Conspicuous Snoop the next turn.
• Mindclaw Shaman (personal choice)
  This is a fun one.
  Most of the cards in this list aren't that impressive by themselves, but with this you can steal big spells from opponent hands and really turn the tides of a game.
  If you have spare mana, you can even jam it into a Grenzo pile and make another player waste the Swords to Plowshares he was keeping to stop your Kiki-Jiki combo.
• Zealous Conscripts
  It comboes with Kiki-Jiki, Mirror Breaker (didn't you take a look at Combos section yet?).
  Most of the times, your path through victory will pass throught finding a way to have Grenzo's power become 3 or more, just to flip this guy.
• Viscera Seer
  Your second sac outlet of choice after Skirk Prospector.
  His pay-off may seem to synergize with Grenzo, but in practice I haven't used it for value that often.
  Once you get a creature into play, you will most likely want it to hold against your opponets' attacks. You'll almost never want to sacrifice it just to scry a card unless it's going to die anyway.
  Of course, that's another story when you're going off, but then you don't care about scry either.
• Priest of Gix
  An old favorite of mine.
  It serves as a mana accelerator in several Doomsday piles (see related section for more details).
  Some people also use Priest of Urabrask, but Priest of Gix is better because it gives you the mana to cast Doomsday when you're under a Moon effect.
• Opposition Agent (competitive slot)
  The black Aven Mindcensor, actually much better. In addition, it comboes with Maralen of the Mornsong.
  Maybe too mean of a play for casual tables, you may want to swap it out for something more fun.
• Maralen of the Mornsong
  You flip it with Grenzo and tutor for Stranglehold or Opposition Agent.
  Not much other use outside of this.
• Ravenous Chupacabra
  It can flipped with Grenzo, it can be fetched by Fleshwrither, it kills a creature. Worth it.
• Xiahou Dun, the One-Eyed (competitive slot)
  It can be flipped by Grenzo (provided you boost him) and can bring back Doomsday from the graveyard.
  This card may be hard to find (still not as hard as Imperial Seal, though), so it may not fit into casual lists.
• Fleshwrither (personal choice)
  It's a bit slow for competitive, but I like it.
  The deck is tailored so that there are many useful 4-drops:
  1. Tuktuk Scrapper against artifacts.
  2. Ravenous Chupacabra against creatures.
  3. Moggcatcher to fetch more goblins.
     ...
• Mikaeus, the Unhallowed
• Master of Cruelties

> Artifacts

TODO

> Enchantments

TODO

> Removals

TODO

> Tutors

TODO

> Other Spells

TODO

> Notable Exclusions

> Sensei's Divining Top

This is probably the first deck I've made without the Top.
It's still a good card, mind you, but I feel it doesn't bring enough to the cause. I just prefer to use the slot for other stuff.
Say you start by casting Sensei's Divining Top, the next turn you're rather willing to cast Grenzo, Dungeon Warden.
Yeah, you could use it on turn 3, provided you have spare mana for it, but the more the game advances, the less it matters what's in your hand and, as a consequence, what's on top of your library.
In the end, you're not going to activating it that much and, if you draw it in late game, it's mostly a dead card.

> Worldgorger Dragon

In the article that inspired this deck, they indeed recommended Worldgorger Dragon as a way to go off without having Grenzo on the battlefield.
At the beginning, I just thought the combo was too convoluted and I preferred to go for the more straightforward Mike & Trike.
As the time passed, I've come to build other decks with Worldgorger Dragon, but I never felt I might reintegrate it here.
In fact, Worldgorger combo is cheaper to deploy with Doomsday, but the point is: this deck is already on the "glass-cannon" category. It doesn't need yet another combo that loses you the game, should the opponent have - say - Swords to Plowshares.
Mike & Trike on the other hand, are cards that you can actually cast outside of the combo and still get some value.

> Braid of Fire

This card seems an automatic inclusion, and indeed was in the deck at the beginning.
I soon realized it didn't fit in with the mana curve, so I removed it.
Let's say you cast Braid of Fire on turn 2 and then Grenzo on turn 3. By the time Grenzo hits the table, the first mana is already gone. Yeah, you get 2 more mana on turn 4, but you're only getting on par with your initial investment.
Ok, let's say you cast Grenzo first, then. On turn 3 you're not going to activate him, because you're busy casting Braid of Fire. On turn 4 you're only netting 1 mana, which is half a Grenzo's activation. Even worse than before.
At the end of the day, Braid of Fire is a card that does nothing for two turns, that's why it's out.

> Junktroller/Canal Dredger/Epitaph Golem

Nearly every other decklist I've seen runs a combination of these three cards. I don't understand why.
First of all, there has to be some creature in your graveyard, which won't necessarily be the case. Even if so, it's likely to be either because it was too big to be flipped by Grenzo, or it has somehow got killed.
If it was too big then, it's probably still too big now, unless you find a way to pump Grenzo first. If it was killed, tipically it was because of a board wipe, so Junktroller and friends are probably in your graveyard too. To me it's unlikely that it got hitted by a spot removal, they're would rather remove Grenzo.
I only see these cards worth getting value out of a creature that you either sacrifice to Ashnod's Altar, or chump-block with each turn. But Ashnod's Altar is 1 card out of 99, you couldn't rely on that, and if you're forced to chump-block each turn chances are you're kind of losing. I don't see you going anywhere with it.
Epitaph Golem is slightly better because it doesn't tap to activate, so it can go infinite with Ashnod's Altar and a token-maker. The problem is: it has power 3, making it not that easy to flip with Grenzo. Therefore it's out too.

> Soldevi Digger/Reito Lantern

These two were originally in the deck because, unlike Junktroller and friends, they can survive a board wipe.
In addition, they both can go infinite with Ashnod's Altar and any creature that makes 2 or more tokens. If the token-maker is also a sac outlet (like for instance Sling-Gang Lieutenant), you can swap the Altar for Mana Echoes and get the same result.
After all it's a nice combo to have, but the problem is: if you don't get either Ashnod's Altar or Mana Echoes into play, the other cards are quite unimpressive. And if I had Demonic Tutor in my hand, I'd rather go for Doomsday than waste my time going wide with tokens.
After some testing, I cut Soldevi Digger for being too narrow, since you can't chose which card to put on the bottom, but I kept Reito Lantern because it could act a a graveyard hate, since it can hit your opponents too.
At some point, I realized I was consistently finding myself with better things to do with those 3 mana. In the end, by the time the Lantern becomes relevant, the game is already in its late stages and the deck isn't likely to survive anyway. I finally cut it too.

> Tel-Jilad Stylus

With Grenzo out, this card can recur any of your creatures for value, although the ones that you actually may be interested in are only a few (I'm thinking about Dockside Extortionist, Goblin Matron, Imperial Recruiter, Priest of Gix, Tuktuk Scrapper and maybe Mindclaw Shaman).
Overall it's a neat trick, although it's unlikely that you get to pull it off consistently. Otherwise, it's a 1-mana artifact that does absolutely nothing.

> Sling-Gang Lieutenant and other token-makers

Many Grenzo lists, especially on the casual level, run a lot of tokens.
I've already mentioned that, if you happen to have Ashnod's Altar or Mana Echoes on the battlefield, you can do crazy things with tokens.
Unfortunately, there aren't that many ways to consistently bring these two enablers into play. So most of the times, you'll be just flipping a bunch of unrelevant critters.
Sling-Gang Lieutenant is actually decent, I've tried it out for a while, but in the end you almost always want to go for Doomsday instead.

> Lake of the Dead

I love the card, many competitive lists play it.
Yes, it's another way to win with Doomsday on turn 3, but you must have two Swamps already on the board to do so. I just don't think this deck runs enough of them to support it.
Also, we're already quite low on lands, and having to sacrifice one can really screw us up.

> Dimir Machinations

This can tutor for Doomsday.
Ok, but everybody gets to know you're trying to combo out. I've already noted that the deck isn't exactly at its best when it comes to protect Doomsday. Also, if for any reason it fizzles, you're pretty much dead.
In the end, I think giving the others a chance to prepare for your combo is too much of a risk.

> Surging Flame, Read the Bones and similar one-shot effects

TODO

> Mogg Raider/Goblin Sledder

TODO