Hi, I'm Gami and this is my Pioneer Soulflayer list! If you want to play a graveyard combo deck that isn't Greasefang, you're in the right place!
This deck is built to maximise the power of Soulflayer and Urborg Scavengers to apply early pressure with a hard to remove threat.

Deck Info:

>Noteable Inclusions:

Vampire of the Dire Moon / Banehound - Blocking vs aggressive decks and/or forcing opponents to trade into it is very strong, especially when we don't mind if it dies. Makes the aggro matchups better game one. May become less relevant if you decide to swing the deck to play more aggro hate mainboard, but in this current version is invaluable.

Ledger Shredder - Shredder can block vs aggo and get damage in against control, all while forcing our opponents to think about how many spells they're casting and furthering or gameplan. A worthy four of in the deck.

Samut, Voice of Dissent - This deck is less all-in on creatures for Soulflayer to delve than most, only having six main exile targets. Zetapla is fairly standard, Samut less so. The reason why, is that almost any combination of Samut and another creature, is fairly powerful, where other options needed three to four different creatures to have been milled to be a real threat without Zetalpa. This means we can run fewer threats overall and have much higher card quality.

Tempest Hart - It may seem bad on paper, but being able to be fetched with Grisly Salvage, being able to discard uncastable cards, and being able to be exiled for trample, a keyword this build lacks a lot of, feels very relevant.

>Noteable Exclusions:

Cragplate Baloth - Hexproof and haste is fine, but only really good as the first Urborg Scavengers target, even then, Scavengers can still be removed in response.

Adult Gold Dragon - A similar story, extra lifelink is good, but I don't think it's better than Samut. Losing the ability to hardcast it over something like the Aetherborns, Vampire of the Dire Moon or Banehound also isn't ideal, when the reason you'd want more lifelink is more aggro in the meta, so early blockers are key.

Neoform / Atraxa, Grand Unifier - There's an argument that the Atraxa Neoform variant is a better deck, but I think we can be equally consistent, if not more so, and pose a bigger, harder to remove threat, even if it doesn't refill our hand.

Founding the Third Path - I like this card a lot, it's able to colour fix, cast two spells in one for Ledger Shredder and reuse spells from the graveyard, a lot of what the deck wants to do. But there's one issue, we want to do as much as we can at instant speed, to be able to hold up countermagic and removal when it matters most, so this being a non-creature sorcery speed spell isn't where we want to be in this deck.

Lands - Eighteen is low, but when the most expensive card we're actually trying to cast in the deck is Urborg Scavengers at three mana and we have 20 ways to filter and draw cards at two mana or less, the deck runs well. Two land hands are perfectly keepable if they have 1-2 dig spells.
The average mana value of the maindeck is 1.56. If we take into account the mana we actually intend to pay for each card. Using Frank Karsten's fairly well respected method for calculating the minimum number of lands needed in a deck, that being 19.59 + (1.90 * average cmc) – (0.28 * cheap card advantage spells), we get 19.59 + (1.90 * 1.53) – (0.28 * 19) = 17.18 lands, so hopefully that gives you some confidence!

>Currently Testing:

Glissa Sunslayer - Alternate pressure against control and destroys grave hate if needed.

Saiba Cryptomancer - Dodging Sheoldred's Edict and any targeted removal, while also being hexproof delve fodder feels great. Worst case can simply be flashed in to chump block and be "discarded" for 1U. May be too complex and a simple counterspell would work better.

Consider - Another one cost dig spell for Ledger Shredder hopefully makes our draws a lot more consistent.

Banehound / Vampire of the Dire Moon - Cheaper than Gifted Aetherborn while hopefully being the same or only slightly worse in most situations.

Rona's Vortex - A more tempo oriented bounce spell with more permanent removal available later.

Sideboard Theory:

> Rakdos Midrange:

Their Problem Cards:

Go Blank - Exiles graveyards, importantly sorcery speed.
Extinction Event - Kills any Soulflayer setup.
Liliana of the Veil - Can force us to sacrifice a Soulflayer, bypassing all our protection.
Unlicensed Hearse - Exiles graveyards at instant speed repeatably.

Game One:

Favoured for us, their only relevant interaction mainboard is Graveyard Trespasser and Bloodtithe Harvester. Both are only at sorcery speed, so can be played around pretty easily.

Post-Board:

A little harder as any number of Extinction Event, Unlicensed Hearse, Liliana of the Veil, Sheoldred's Edict, Go Blank and Necromentia come in. These all get discarded by Thoughtseize and countered by Stubborn Denial.
Be careful if Sacrifice reveals Jegantha, the Wellspring game one but not game two, this means they likely have brought in Lelyline of the Void.

Changes:

In:
2x Abrupt Decay - Hitting a resolved threat is still necessary.
1x Drown in the Loch - As the game goes later this will be able to answer most, if not all, threats that Rakdos can throw at us.
1x Glissa Sunslayer - Removing Fables and planeswalkers is very useful. Difficult to block, a good source of card advantage while also providing good keywords for the Soulflayer pile.

Out:
2x Rona's Vortex - Few creatures that drastically affect our gameplan, don't want to give them resources back to hand.
1x Otherworldly Gaze - While this is good, it doesn't actually draw us a card, trimmed one.
1x Tempest Hart - Going down cards is slightly worse here as Rakdos will be a game of attrition.

> Nykthos Ramp:

Their Problem Cards:

Karn, the Great Creator - Access to sideboard and silver bullets game 1.
Storm the Festival - Generates a lot of advantage that is difficult to come back from.
Nykthos, Shrine to Nyx - Nykthos is manageable as long as we can keep devotion off the board and answer whatever they play.
Kiora, Behemoth Beckoner - Untaps Nykthos and generates tons of mana.

Game One:

Tough, but winnable. If they get a good hand, we have to interact early or we lose, if they get a normal hand, interacting early makes it likely we win.
Keep them off high devotion if you can, don't focus desperately hard on getting a max-power Soulflayer, anything that fights a Cavalier and lives is good enough.
Vampire of the Dire Moon and Banhound really help in applying pressure as they have to choose between sacrificing a creature to block and lose devotion or let their planeswalkers start taking hits. Glissa also helps with this post-board.

Post-Board:

Slightly better, but still not great. Nykthos almost never sideboards though, making Game 2-3 almost objectively better for us.
Assassin's Trophy is mostly there to disrupt their combo, hitting any Planeswalker or Nykthos itself. Can kill a Cavalier in a pinch if we need to push damage through.

Changes:

In:
2x Duress - Throwing away a Karn, Kiora, Storm the Festival or whatever other bomb they happen to have in their hand is great for us here, slow them down enough to get out a Soulflayer.
2x Abrupt Decay - Removes creature devotion or Kiora, good for keeping them on their combat plan.
1x Glissa Sunslayer - Can remove their ramp enchantments, kill their planeswalkers, get devotion off the board if they attack or block.
1x Drown in the Loch - While unlikely to be good early game, in the mid to late game this can snag a Karn or Storm the Festival, remove a threat and hopefully get us back into a winning position.

Out:
2x Ledger Shredder - Blocking won't be much use unless we put 2+ counters on it, attacking won't be much use as Cavalier of Thorns and Polukranos Reborn have reach. Don't want to completely cut our discard outlets though.
2x Striped Riverwinder - Outside of Karn wish targets, they have no way to remove a Soulflayer, and most of their wishboard doesn't deal with it well, going down a few hexproof creatures is safe here.
2x Consider - Cutting down on Ledger Shredders means we need fewer one mana cantrips to connive.

> Azorius Control:

Their Problem Cards:

Farewell - Exiles any Soulflayer setup.
Rest in Peace - Shuts down our entire gameplan
Absorb / Make Disappear - Counters our creatures, worst with Soulflayer who delves as a cost.

Game One:

Do not overextend, they have quite a few blowout cards, take your time, don't rush. Force them to boardwipe Shredders, Vampires and Banehounds, cast instants when they tap out at end step. This is not a race.
Don't be afraid to cast Urborg Scavengers early with no value, if you think you can get them to resolve and start getting damage in, do. If you can start exiling relevant things as well, even better.

Post-Board:

Rest in Peace absolutely destroys our gameplan, so try to always have removal or counters for it. Other than that, very similar to Game One but we have more disruption and they have Rest in Peace.

Changes:

In:
3x Mystical Dispute - Interacting early is key here, hitting RiP or resolving something through an Absorb is great.
2x Duress - For shredding their hand, keeping them low on resources and trying to pick a hole in their defences.
1x Glissa Sunslayer - An additional threat that can kill Planeswalkers, draw cards and remove graveyard hate.
1x Drown in the Loch - Can hit a boardwipe, Teferi, or other threat later in the game.

Out:
2x Vampire of the Dire Moon - Lifelink doesn't help here and they're not going to beat down on their own.
2x Otherworldly Gaze - The earlier turns will be spent interacting, so going down some Gazes here feels safe.
1x Tempest Hart - With slightly fewer uncastable cards, we need slightly fewer ways to discard them.
1x Consider - Aiming to have a slightly higher card quality when playing against control.
1x Samut, Voice of Dissent - Going down one threat feels fair here, needing to run more interaction and removal means the game will go longer, giving us time to mill a threat even if we're only on 5 major targets instead of 6.

> Lotus Combo:

Their Problem Cards:

Lotus Field - Gives them the mana to win fast.
Emergent Ultimatum - Tutors for their combo
Languish - Kills any Soulflayer setup.

Game One:

This is why the Stubborn Denials are mainboard, counter their spells, Thoughtsieze their hand, apply pressure as fast as possible.

Post-Board:

Slightly better, as we have fewer dead cards, but the same still applies. Disruption and pressure wins games here.

Changes:

In:
3x Mystical Dispute - Catches a lot of important spells, most notably Emergent Ultimatum and Pore Over the Pages.
2x Duress - Taking draw / search spells and untap cards leaves them low on resources and buys us time to execute our plan.

Out:
2x Vampire of the Dire Moon - Deathtouch and lifelink don't help here and it's hard to argue that chip damage with a 1/1 is relevant. Playing something that does nothing to stop their gameplan, or further ours is an easy cut.
2x Striped Riverwinder - Very little removal coming from Lotus so we can get away with less hexproof.
1x Otherworldly Gaze - Against Lotus, interaction is key, Gaze not actually drawing us a card means we shave one here.

>Abzan Greasefang:

Their Problem Cards:

Greasefang, Okiba Boss - Reanimates and crews vehicles.
Parhelion II - Cheated into play.
Liliana of the Veil - Can force us to sacrifice a Soulflayer, bypassing all our protection.

Game One:

Getting a strong Soulflayer is borderline game over. Both decks combo at similar speeds, but we have seven threats and they only have four, some are running six if you count Eldritch Evolution or Traverse the Ulvenwald, but these take much more time than the dreaded turn three Greasefang.

Post-Board:

They have more removal sideboard, with Liliana of the Veil and sometimes Vanishing Verse, so now the requirement for an immoveable Soulflayer is hexproof, indestructible and to have one other creature on board. Matchup feels like it leans in our favour.

Changes:

In:
3x Ray of Enfeeblement - Kills Greasefang.
2x Abrupt Decay - Kills Greasefang and a variety of other things that stop our gameplan like Unlicensed Hearse.
1x Assassin's Trophy - Used mostly as a second copy of Abrupt Decay, but can also hit Leyline of the Void if they have it.
1x Drown in the Loch - One of the best matchups for Drown, they will almost certainly have three or more cards in their graveyard when they cast Greasefang so we can deal with it efficiently.

Out:
2x Striped Riverwinder - They have limited removal so most instances of hexproof can come out.
2x Vampire of the Dire Moon - This match will be won with a few big combat steps, not a 1/1 on the ground.
2x Tempest Hart - We need to be going faster and digging harder than Indulgence lets us.
1x Stubborn Denial - While there are a few non-creature spells, their most important one is Greasefang, shaved one here.

> Creativity (Temur / Izzet):

Their Problem Cards:

Indomitable Creativity - Main path to them winning the game
Make Disappear - Hits creatures, can't be stopped by a single counterspell if they cast it with Casualty.
Divide by Zero - Counterspell or bounce spell, makes hexproof important.

Game One:

Temur needs to get to five mana and two tokens to flip into Worldspine Wurm and Xenagos, God of Revels to one-shot the opponent. Izzet only needs four and one, but their payoff is much less impactful.
Soulflayer can combo faster than creativity and then play the control game, but there's an element of luck to it, the matchup isn't terrible, but you need to be careful. Either resolve Soulflayer fast and close the game, or wait until they're low on resources and capitalise.
The plan game one is simply to resolve a Soulflayer, doesn't have to be particularly strong, hexproof / indestructible + doublestrike will do. Once we have pressure, hold up mana and counter any attempts to cast Indomitable Creativity.

Post-Board:

After boarding it's quite similar. Take your time and be ready for a fight on the stack.

Changes:

In:
3x Mystical Dispute - More disruption early, hits their counters and makes sure our threats resolve.
2x Duress - Taking their combo pieces or interaction, either slowing them down or poking a hole for us to combo through.

Out:
2x Vampire of the Dire Moon - Deathtouch and lifelink don't help against combo control.
2x Striped Riverwinder - There's less relevant removal in the matchup and most is damage based. Happy to cut a copy of hexproof.
1x Otherworldly Gaze - This matchup will be about interaction, so trimming something that doesn't actually put cards in hand is the call here.

>Mono-White Humans:

Their Problem Cards:

Brutal Cathar - Exiles a non-hexproof Soulflayer. Even if we get it back, it loses the keywords.
Rest in Peace - Shuts down our Soulflayer gameplan.
Thalia, Guardian of Thraben - as a low curve deck with few lands, adding 30-50%+ to the cost of our spells hurts.

Game One:

Has the potential to be one of our worst matchups, I decided to gear the maindeck towards combo more and the sideboard towards aggro, you might prefer it the other way around, mostly a meta call.
Will be difficult to win this one unless you run pretty well on your mill and draw. They can't beat a full Soulflayer setup, but they will not give little time to get there. Prioritize lifelink, hexproof and blockers first. hope to close the gates before they kill us.

Post-Board:

Quite a bit better with 9 sideboard cards in. Same as game one, prioritize lifelink and hexproof to make an impossible to remove Soulflayer as soon as possible.

Changes:

In:
3x Ray of Enfeeblement - Hits every creature in the deck
2x Path of Peril - A way for us to stabilise if they're going too fast.
2x Abrupt Decay - Hits every creature and Rest in Peace.
1x Glissa Sunslayer - Difficult to block and attack into. Removes RiP if they find it.

Out:
4x Thoughtseize - Hand interaction is much less important in the aggro matchup.
2x Stubborn Denial - They have few noncreature spells, much less useful here.
2x Striped Riverwinder - They have little removal so shaved two hexproof sources.

>Spirits (Mono-Blue / Azorius / Bant):

Their Problem Cards:

Lofty Denial - Easily counters a Soulflayer
Geistlight Snare - Easily counters a Soulflayer
Rest in Peace - Shuts down our Soulflayer gameplan.

Game One:

As with most aggro decks, they can't beat a resolved Soulflayer with good keywords, they offer less pressure than other aggro decks, but significantly more disruption.
Game one should be relatively straightforward, if difficult, block with Ledger Shredders, fight through disruption, resolve a Soulflayer when you can, win from there.

Post-Board:

Mostly the same, apart from the vague threat of turn two Rest in Peace, if this happens we can block with Shredders and try to gain life back with Vampires and Banehound. It's harder, but not impossible. Most lists seem to have steered away from RiP, so hopefully your Spirits opponent has too.

Changes:

In:
3x Mystical Dispute - Will hit most, if not all of their spells.
2x Path of Peril - A way for us to stabilise if they're going too fast.
2x Abrupt Decay, - Most lists seem to have stopped playing Rest in Peace, but this deals with that, as well as all of their creatures, through counterspells.

Out:
2x Stubborn Denial - Even though they have lots of disruption, they're a tempo deck, creatures are their main plan, Mystical Disputes are our counter of choice.
2x Consider - Needing to interact early means consider is slightly less good, cut both.
2x Striped Riverwinder - They run limited removal. We should aim to have counterspells up or have already discarded their tempo plays, so going down on other angles of protection is fine.
1x Tempest Hart - Need to dig for answers and delve targets faster than this allows.

>Mono Red Aggro:

Their Problem Cards:

Wizard's Lightning - Kills both of our two drop x/3s
Kari Zev's Expertise - Can steal a Soulflayer without a full setup.
Rampaging Ferocidons - Stops our lifegain if we have it.

Game One:

They will be fast, but have literally no way to remove a resolved Soulflayer, if we get indestructible and lifelink, it's basically game over.

Post-Board:

They can bring in Rampaging Ferocidons to stop us gaining life, but even so, eight damage a turn is hard to race, especially if they're losing attackers running into a Soulflayer with vigilance.

Changes:

In:
2x Path of Peril - A way for us to stabilise if they're going too fast.
2x Abrupt Decay - While not ideal, forcing them to find another creature is relevant tempo against a very fast deck.
1x Glissa Sunslayer - Very hard to attack into.

Out:
4x Thoughtseize - The life loss hurts. Good disruption, but not where we want to be.
1x Striped Riverwinder - Very little that can kill a Soulflayer, trimmed one.

*Less Tested Matchups

> Gruul Midrange:

Their Problem Cards:

Skysovereign, Consul Flagship - Very evasive to all of our removal as it'll most likely only be a creature on their turn. Needs a Zetalpa Soulflayer to get through it.
The Akroan War - Will steal a non-hexproof Soulflayer for multiple turns.

Changes:

In:
2x Abrupt Decay - Destroys every creature in the deck.
1x Assassin's Trophy - At the cost of a basic land, kills any threat, the panic button.
1x Glissa Sunslayer - A powerful blocker with additional upside.

Out:
2x Stubborn Denial - They're mostly creature based, while they have some enticing targets, it's not worth it to have a mostly dead card for the small chance of a blowout.
2x Striped Riverwinder - The biggest targeting threat to worry about is The Akroan War, but we can hopefully use our removal and disruption to make sure it never sticks around for long.

> Selesnya Angels:

Their Problem Cards:

All the angels have flying, so our usual evasion won't be as good.
Deafening Silence - This isn't as bad as it looks as we can play a lot at instant speed, removed fairly easily it gets too taxing.
Shapers' Sanctuary - To slow them down enough to set up Soulflayer, we're going to need to remove their creatures, Sanctuary gaining them a card each time we do is pretty bad.
Rest In Peace - Shuts down the graveyard.

Changes:

In:
3x Ray of Enfeeblement - Removes any creature for one mana, great way to stop their early developments.
2x Abrupt Decay - Removes every non-land permanent in their deck, including RiP
1x Assassin's Trophy - Used mostly as a second copy of Abrupt Decay

Out:
2x Striped Riverwinder - Very little removal that hits Soulflayer, Scavengers is a bit more vulnerable, but cutting some Hexproof doesn't feel too bad.
2x Stubborn Denial - They have a few good targets, but mostly dead.
2x Vampire of the Dire Moon - No blocking will be done as all their threats fly.

>Izzet Phoenix:

Their Problem Cards:

Thing in the Ice - Can force us to return a Soulflayer to our hand if it flips.
Disdainful Stroke - Counters our Soulflayer.

Changes:

In:
3x Mystical Dispute - Will hit all of their counters
2x Abrupt Decay - Hitting Thing in the Ice is key as it's one of their only ways of stopping a Soulflayer
1x Assassin's Trophy - Essentially a second copy of Abrupt Decay.

Out:

2x Otherworldly Gaze - Needing to interact early means Gaze is slightly less good, trimmed two.
2x Stubborn Denial - Bringing in three Mystical Dispute means we can afford to trim some amount of the worse counterspell.
2x Striped Riverwinder - They run limited removal. We should aim to have counterspells up or have already discarded their tempo plays, so going down on other angles of protection is fine.

>Five-Colour Midrange:

Their Problem Cards:

Fires of Invention - One of the possible engines of the deck.
Bring to Light - One of the possible engines of the deck.
Rest in Peace - Shuts down our entire gameplan.
Various targeted exile effects - Need Hexproof.

Changes:

In:
2x Abrupt Decay - Removes their early enchantments, notably RiP.
1x Assassin's Trophy - Kills the bigger threats if they have time to stabilise.
1x Glissa Sunslayer - Removes their bigger enchantment and threats.
1x Drown in the Loch - Mid to late game blowout potential, can remove most of their value engines happily.

Out:
2x Vampire of the Dire Moon - Chip damage isn't relevant.
1x Ledger Shredder - Doesn't put pressure on fast enough, not awful in the matchup, but space has to be made somewhere.
1x Consider - Not needing to go quite as fast means consider can come out for more meaningful cards.
1x Samut, Voice of Dissent - No protection makes her less valuable, longer games means we can afford to cut some delve targets.

>Boros Convoke:

Their Problem Cards:

Gleeful Demolition - Essentially Dark Ritual in this deck, insane acellarant.
Venerated Loxodon - Gives a buff to their creatures and adds a medium sized body.
Reckless Bushwhacker - Turns a small push into a lethal attack.
Knight-Errant of Eos - Draws them cards and allows them to keep up pressure.

Changes:

In:
3x Ray of Enfeeblement - Removes their bigger threats
2x Path of Peril - Will hit all of their tokens.

Out:
2x Tempest Hart - Doesn't see as many cards as we need it to in this race.
2x Striped Riverwinder - Next to no removal in their deck. A Giant Killer is all that we need to worry about.
1x Otherworldly Gaze - The first few turns will need interaction, so we can go down on our one drop dig spells.

>Boros Pia Aggro:

Their Problem Cards:

Chained to the Rocks - Not awful as we have enchantment removal and hexproof, but something to watch out for.
Pia Nalaar, Consul of Revival - Goes very wide if left unchecked.

Changes:

In:
2x Path of Peril - Will hit all their creatures if they're getting too far ahead.
2x Abrupt Decay - Some decks run Rest In Peace, this hits that while also removing creatures if needed. Also hits Invasion of Gobakahn from the board.
1x Assassin's Trophy - A second copy of Abrupt Decay here.

Out:
2x Thoughseize - Hitting a creature from their opener is nice, but is a terrible topdeck late game
2x Stubborn Denial - A lot of their cards aren't worth countering as they have such high card velocity.
1x Striped Riverwinder - Limited removal means we can trim the fourth hexproof effect

>Lotus Control

Their Problem Cards:

Strict Proctor - Slows down Urborg Scavengers, allows them to play Lotus Field with no downside.
Discontinuity - We need to be careful doing things on their end step as they can just exile our spell for two mana, as with regular control, we have to wait until we have counterspell backup or they tap out before trying anything important.
Sunfall / Farewell - Three exile-based wraths mainboard is difficult, watch out for these and be ready to fight them.
Rest in Peace - Shuts down our gameplan hard.

Changes:

In:
3x Mystical Dispute - Interacting early is key here, hitting RiP or resolving something through an Absorb is great.
2x Duress - For shredding their hand, keeping them low on resources and trying to pick a hole in their defences.
1x Glissa Sunslayer - An additional threat that can kill Planeswalkers, draw cards and remove graveyard hate.

Out:
2x Vampire of the Dire Moon - Lifelink doesn't help here and they're not going to beat down on their own.
2x Otherworldly Gaze - The earlier turns will be spent interacting, so going down some Gazes here feels safe.
1x Banehound - Fine delve target, but not great outside of that.
1x Samut, Voice of Dissent - Going down one threat feels fair here, needing to run more interaction and removal means the game will go longer, giving us time to mill a threat even if we're only on 5 major targets instead of 6.

>Archfiend Combo

Their Problem Cards:

Archfiend of the Dross / Metamorphic Alteration - these, together, can make us lose the game on our upkeep.
Extinction Event - Can remove a Soulflayer no matter what we do. Hold your counters for these if you can.

Changes:

In:
3x Mystical Dispute - Creature-light matchup, countering wraths and draw spells will be important.
2x Duress - Discards their Fable of the Mirror Breakers, Metamorhpic Alteration etc.
2x Abrupt Decay - Removes their value enchantments, or stops us from dying to an Alteration.
1x Assassin's Trophy - Another copy of Abrupt Decay that can also kill an Archfiend.

Out:
2x Vampire of the Dire Moon - Lifelink doesn't help here and they're not going to beat down on their own.
2x Otherworldly Gaze - The earlier turns will be spent interacting, so going down some Gazes here feels safe.
2x Striped Riverwinder - Despite the threat of Metamorphic Alteration, very little else actually removes our creatures, shaved one.
1x Stubborn Denial - Mystical Dispute will get the job done better here, trimmed one.
1x Samut, Voice of Dissent - Going down one threat feels fair here, needing to run more interaction and removal means the game will go longer, giving us time to mill a threat even if we're only on 5 major targets instead of 6.