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 / Gifted Aetherborn - Blocking vs aggressive decks and/or forcing opponents to trade into these 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 they're 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.

Ephara's Dispersal - A card that interacts with the opponent while also furthering our gameplan.

>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 17 ways to filter and draw cards at two mana or less, (more if you count Ephara's Dispersal, although I don't, as it's more of a removal spell), we can run a comparatively low number of lands while still being consistent. Two land hands are perfectly keepable if they have 1-2 dig spells.
The average mana value of the maindeck is 1.50. 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 selection spells), we get 19.59 + (1.90 * 1.50) – (0.28 * 17) = 17.68 lands, so hopefully that gives you some confidence!

>Currently Testing:

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. Especially useful when double spelling for Ledger Shredder.

Ephara's Dispersal - Being able to play an interactive card that also furthers our gameplan feels very strong, even if relatively restrictive.

Sideboard Theory:

> Rakdos Midrange / Sacrifice:

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.
Be careful if Sacrifice reveals Jegantha, the Wellspring game one but not game two, this means they likely have brought in Leyline of the Void.
Gameplan is mostly the same, but this time we can answer their board a little more efficiently.

Changes:

In:
3x Abrupt Decay - Hitting a resolved threat is still necessary.
1x Assassin's Trophy - Can remove Sheoldred, the Apocalypse or any other problem permanent. Gives them a land, but a land should always be much less scary than the thing it removes.
1x Glissa Sunslayer - Removing Fables and planeswalkers is very useful. Difficult to block, a good source of card advantage while also providing keywords for the Soulflayer pile.

Out:
2x Thoughtseize - While hand disruption is good, it's a terrible draw whem both players are low on resources.
1x Ephara's Dispersal - Bouncing creatures back to hand is significantly worse than destroying them in the attrition match.
1x Otherworldly Gaze - Going down on cards isn't what we want here, shaved one.
1x Banehound - No deathtouch means that this is a much less threatening blocker.

> 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.

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:
3x Abrupt Decay - Removes devotion or Kiora, keeps them on their combat plan.
2x Duress - Taking away their planeswalkers or other big plays can be very impactful.
1x Glissa Sunslayer - Can remove their ramp enchantments, kill their planeswalkers and get devotion off the board if they decide to block.
1x Assassin's Trophy - Removes any permanent that is being a threat.

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 Stubborn Denial - They will often have enough to pay 1 and if we have ferocious online, were likely far ahead regardless.
1x 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 hexproof creatures is safe here.
1x Ephara's Dispersal - They don't have to attack to win, so this will be online less often than we want.
1x Banehound - Lifelink and haste aren't key in this matchup, shaved for more relevant cards.

> 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 Assassin's Trophy - Removes any big threat if they manage to resolve one.

Out:
2x Vampire of the Dire Moon - Lifelink doesn't help here and they're not going to beat down on their own.
2x Fatal Push - Next to no targets in their deck.
1x Ephara's Dispersal - Next to no targets.
1x Banehound - Not enough of a threat and keywords aren't the most useful

> 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:

Thoughtsieze their hand, apply pressure as fast as possible. We have relatively few ways to deal with their combo mainboard.

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.
1x Assassin's Trophy - If they board in Zacama or other big threats, we want at least one thing that can remove it. Can also hit Thespian's Stage in response to it copying Lotus.

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 Fatal Push - Nothing to target.
1x Striped Riverwinder - Very little removal coming from Lotus so we can get away with less hexproof.
1x Ephara's Dispersal - Almost no targets in the deck.

>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.

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 Fatal Push - Doesn't kill Greasefang so these come out.
2x Stubborn Denial - Few important non-creature spells. Removal prioritized over counters.

> 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 Fatal Push - Almost nothing to hit outside of Fable tokens.
1x Striped Riverwinder - There's less relevant removal in the matchup and most is damage based. Happy to cut a copy of hexproof.

>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.
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 plenty of 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.
3x Abrupt Decay - Hits every creature and Rest in Peace.
2x Gifted Aetherborn - Makes combat difficult, another two sources of lifelink for Soulflayer.

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.
1x Otherworldly Gaze - Not adding to the board when we need to race makes Gaze slightly worse.
1x Consider - Need to fill the graveyard faster than this allows.

>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 Ephara's Dispersal - Bouncing their creatures while letting us surveil seems strong.
2x Abrupt Decay - Removes RiP if they have it, safely destroys any threat as it can't be countered.

Out:
4x Thoughtseize - Their creature are their card draw, so removing their blockers is our form of resource denial here.
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.
1x Consider - Doesn't full the graveyard as fast as we need here.

>Mono Red Aggro:

Their Problem Cards:

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:
3x Abrupt Decay - While not ideal, forcing them to find another creature is relevant tempo against a very fast deck.
2x Gifted Aetherborn - Makes combat difficult and getting lifelink on a Soulflayer wins us the game.

Out:
4x Thoughtseize - The life loss hurts. Good disruption, but not where we want to be.
1x Consider - Need to be going slightly faster than Consider let's us.

*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:
3x Abrupt Decay - Destroys every creature in the deck.
2x Gifted Aetherborn - Makes combat difficult and lifelink helps us stabilise.
1x Assassin's Trophy - For destroying Skysovereign or The Akroan War

Out:
2x Otherworldly Gaze - We can afford to go slightly slower and prioritize keeping cards in hand here.
2x Thoughtseize - They're a very resistant deck, so throwing away a card isn't as impactful.
1x Banehound - No deathtouch means it's a less impactful blocker.
1x Consider - Need to add to the board a little more.

> 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.
3x Abrupt Decay - Removes every non-land permanent in their deck, including RiP
1x Assassin's Trophy - Used mostly as another 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 Vampire of the Dire Moon - No blocking will be done as all their threats fly.
2x Stubborn Denial - They have a few good targets, but mostly dead.
1x Ephara's Dispersal - Bouncing a creature back to hand lets them replay it and trigger all their lifegain again, not good for us.

>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 Soulflayer.

Out:
2x Otherworldly Gaze - Needing to interact early means Gaze is slightly less good, trimmed two.
2x Stubborn Denial - Bringing in Mystical Dispute means that we can afford to cut the worse counterspell.
1x 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:
3x 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.

Out:
2x Vampire of the Dire Moon - Chip damage isn't relevant.
2x Fatal Push - They rarely have creatures small enough to hit with this.
1x Consider - Not needing to be quite as card efficient means Consider can come out for cards that dig deeper.

>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 one drops or bigger threats.
2x Gifted Aetherborn - Extra sources of lifelink help us stabilise and make it harder for them to put up as much if a clock

Out:
2x Striped Riverwinder - Next to no removal in their deck. A Giant Killer is all that we need to worry about.
2x Stubborn Denial - Easy to play around and only really hits Gleeful Demolition.
1x Ephara's Dispersal - Giving them the chance to play their convoke creature again is bad for us.

>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:
3x 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.
2x Gifted Aetherborn - Extra lifelink slows down their clock or wins us the game if we get an immoveable Soulflayer.

Out:
4x Thoughtseize - They are a resilient deck with lots of card advantage, Thoughtseize loses it's value.
1x Consider - Doesn't full the grace as fast as we want here.

>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.
1x Assassin's Trophy - Hits any of their Planeswalkers or Thespian's Stage if they try to copy Lotus Field.

Out:
2x Vampire of the Dire Moon - Lifelink doesn't help here and they're not going to beat down on their own.
2x Fatal Push - While this can remove Strict Proctor, it doesn't hurt our gameplan too much and Push is dead everywhere else
1x Ephara's Dispersal - They will rarely be attacking enough to trigger this early.
1x Otherworldly Gaze - The earlier turns will be spent interacting, so going down some Gazes here feels safe. Don't need to fill the graveyard as fast.
1x Banehound - Not enough of a threat and keywords aren't the most useful

>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.
1x Assassin's Trophy - Can remove any permanent if and when we need it.

Out:
2x Vampire of the Dire Moon - Lifelink doesn't help here and they're not going to beat down on their own.
2x Fatal Push - Very few targets for Push here
1x Striped Riverwinder - Outside of Alteration, very little actually can remove our creatures, trimmed one.
1x Banehound - While haste and lifelink are nice, neither are required here.