Grenzo, Key Master (EDH / Commander)

"Grenzo, Dungeon Warden" is unique from a lot of other commanders in a number of ways and has many of the most powerful tools in the game in his back pocket. The biggest issue for Grenzo is that the deck lacks predictability, even to the deck's pilot.

Advantages:
Doesn't care about card draw and is fine with discarding
Cheats mana costs
*Doesn't mind if things die

Disadvantages:
Weak to grave hate
Weak to removal of Commander
Inherently Random
Struggles to use Non-creatures

I've divided this deck into several sections, each one has some cards which have crossover, but I've chosen the locations of those cards to best communicate the primary function of the card in the deck. The category labeled "Main" is a collection of things which there aren't enough of to warrant a category for them, but these cards are no less important to the deck.

Land and Utility Land:
These two categories are being merged for explanation because they're pretty simple. Grenzo relies heavily on his activated ability, and the ability is so cheap to activate that every bit of speed in your lands is important. Lands that come into play tapped are a huge risk that they'll grant you one less activation of Grenzo that turn, and given how powerful a single activation can be, its important to get everything you can. Additionally people who have played against Grenzo before are likely to target him out for removal because one activation can chain into several more. For this reason, entering tapped lands are kept to a minimum, and the deck has a higher rate of basics than many other two color decks. In addition since the deck is only two colors, and Grenzo's ability only requires colorless mana, once Grenzo is cast colors will matter fairly infrequently.

Ramp and Mana Generation:
As stated before even a single extra mana on a turn can result in an extra activation for Grenzo, so its very important that Grenzo has a good number of accelerators so that he can activate as many times in a turn as possible. These cards are extra important because in this particular deck Grenzo wants to be played as a 6/6 which means that for a good number of turns you probably wont play much of anything, and that each time Grenzo is removed he will become significantly harder to cast at the 6/6 point.

Some of the cards in this section are token generators of some kind. These combo with the sacrifice outlets sprinkled across the deck, and in some cases may even sacrifice themselves for additional mana. With a Heartstone, Ashnod's Altar, and Grenzo on the field Grenzo has the potential to run through and play almost every creature in the deck in a single turn, so there is a lot of potency to be had in this section.

Burn:
Other than straight aggro this is Grenzo's most effective way of finishing a game. Through some combination of doing what Grenzo already does best, and the cards in this category he can burn the table to the ground. Some of these things are ETB effects and the important thing to remember about Grenzo regarding ETB effects is that you have to be willing to accept any outcome when you activate Grenzo's ability. The randomness of the ability means that any of the effects could happen at any point in the game, and indeed might. Some of these effects can be game ending at the right moment. Other times you'll whiff and the burn will be negligible, in these cases wait until it will be very strong to do so, and then recur your burn and do it again.

Haste Givers:
This section is very important and arguably should be larger depending on the rest of the deck. This particular deck doesn't have many tap effects on creatures, so it's less important, but Haste is the difference between winning and getting hosed by a board wipe. For Grenzo a ill-timed board wipe can lose the game easily because it can take time to get back on your feet. Depending on your group its unlikely you'll see someone holding up 4 mana every turn just in case you go off, but once you've gone off you can bet that almost no one will have any qualms spending their turn to save the game from your run away victory, making haste the biggest tool you have for dealing with players you suspect may be holding on to something dangerous.

Removal:
Grenzo favors creatures heavily. His ability will dump everything but creatures straight into the graveyard, so the removal options available to Grenzo are few and far between, all stacked on creatures who will come in at random times, and sometimes they will even whiff. Removal is not in Grenzo's wheel house despite his colors, and as a result the package is much smaller than usual.

Card Advantage:
Grenzo has a unique take on card advantage compared to most commanders. Because Grenzo can play from the bottom of his library he really doesn't care much about his hand, and draw loses much of its value. In fact in many scenarios drawing new cards would be bad. Grenzo wants cards on the bottom of his library so that he can pay much less to cast them than he would otherwise. Some draw is still good because not all of the deck is creatures, but allowing Grenzo to discard creatures brings him great fortune as it makes them easier to cast than they would be in his hand.

Grenzo uses discard effects and sacrifice to control his opponents rather than stack control or direct removal. Wheeling puts cards in the graveyard for Grenzo to use, but it puts opponent's cards in the graveyard where they're harder to access for many other decks. This also allows Grenzo to decide when to wheel, and when to play the few non-creatures the deck has. Once he has done what he wants, its time for everyone to wheel.

Controlling the Grave/Bottom of the Library:
Grenzo's ability is somewhat unique in that he must put things on the bottom of his library in order to decide what to play. Randomness is fine most of the time, but sometimes you need to recur Gray Merchant of Asphodel a few times, or fetch something that was pitched into the grave by an earlier wheel. These cards either put things onto the bottom of the library, allow Grenzo to do so by scrying, or allow Grenzo to recover items from the grave that he cant use his ability to bring out.