Breathkeeper Seraph

Flying, soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Breathkeeper Seraph is paired with another creature, each of those creatures has "When this creature dies, you may return it to the battlefield under its owner's control at the beginning of your next upkeep."

Plains

Hunted Bonebrute

Menace
When this creature enters, target opponent creates two 1/1 white Dog creature tokens.
When this creature dies, each opponent loses 3 life.
Disguise {1}{B}

Death Tyrant

Menace
Negative Energy Cone — Whenever an attacking creature you control or a blocking creature an opponent controls dies, create a 2/2 black Zombie creature token.
{5}{B}: Return this card from your graveyard to the battlefield tapped.

Skeletal Wurm

Blind Hunter

Flying
Haunt (When this creature dies, exile it haunting target creature.)
When this creature enters or the creature it haunts dies, target player loses 2 life and you gain 2 life.

Drudge Skeletons

{B}: Regenerate this creature. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Lim-Dûl's High Guard

First strike
{1}{B}: Regenerate this creature.

Barrier of Bones

Defender
When this creature enters, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Briarhorn

Flash
When this creature enters, target creature gets +3/+3 until end of turn.
Evoke {1}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Carrionette

{2}{B}{B}: Exile this card and target creature unless that creature's controller pays {2}. Activate only if this card is in your graveyard.

Daxos, Blessed by the Sun

Daxos's toughness is equal to your devotion to white. (Each {W} in the mana costs of permanents you control counts toward your devotion to white.)
Whenever another creature you control enters or dies, you gain 1 life.

Ghastly Death Tyrant

When this creature enters, choose one —
• Disintegration Ray — Destroy target enchantment an opponent controls. You lose life equal to its mana value.
• Death Ray — Creatures you control gain deathtouch until end of turn.

Ajani, Valiant Protector

+2: Put two +1/+1 counters on up to one target creature.
+1: Reveal cards from the top of your library until you reveal a creature card. Put that card into your hand and the rest on the bottom of your library in a random order.
−11: Put X +1/+1 counters on target creature, where X is your life total. That creature gains trample until end of turn.

Riftsweeper

When this creature enters, choose target face-up exiled card. Its owner shuffles it into their library.

Abyssal Gorestalker

When this creature enters, each player sacrifices two creatures of their choice.

Absolver Thrull

Haunt (When this creature dies, exile it haunting target creature.)
When this creature enters or the creature it haunts dies, destroy target enchantment.

Clattering Augur

This creature can't block.
When this creature enters, you draw a card and you lose 1 life.
{2}{B}{B}: Return this card from your graveyard to your hand.

Sentry of the Underworld

Flying, vigilance
{W}{B}, Pay 3 life: Regenerate this creature.

Adipose Offspring

Emerge {5}{W} (You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's mana value.)
When this creature enters, create a 2/2 white Alien creature token. If this creature's emerge cost was paid, instead create X of those tokens, where X is the sacrificed creature's toughness.

Dawnfluke

Flash
When this creature enters, prevent the next 3 damage that would be dealt to any target this turn.
Evoke {W} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Cult Conscript

This creature enters tapped.
{1}{B}: Return this card from your graveyard to the battlefield. Activate only if a non-Skeleton creature died under your control this turn.

Caldaia Guardian

Whenever this creature or another creature you control with mana value 4 or greater dies, create two 1/1 green and white Citizen creature tokens.
Blitz {2}{G} (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)

Athreos, God of Passage

Indestructible
As long as your devotion to white and black is less than seven, Athreos isn't a creature.
Whenever another creature you own dies, return it to your hand unless target opponent pays 3 life.

Foundation Breaker

When this creature enters, you may destroy target artifact or enchantment.
Evoke {1}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Abzan Banner

{T}: Add {W}, {B}, or {G}.
{W}{B}{G}, {T}, Sacrifice this artifact: Draw a card.

Corpses of the Lost

Skeletons you control get +1/+0 and have haste.
When this enchantment enters, create a 2/2 black Skeleton Pirate creature token.
At the beginning of your end step, if you descended this turn, you may pay 1 life. If you do, return this enchantment to its owner's hand. (You descended if a permanent card was put into your graveyard from anywhere.)

Belfry Spirit

Flying
Haunt (When this creature dies, exile it haunting target creature.)
When this creature enters or the creature it haunts dies, create two 1/1 black Bat creature tokens with flying.

Swamp

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)

Abyssal Gatekeeper

When this creature dies, each player sacrifices a creature of their choice.

Tenacious Dead

When this creature dies, you may pay {1}{B}. If you do, return it to the battlefield tapped under its owner's control.

Wretched Bonemass

Wretched Bonemass's power and toughness are each equal to the total power of the exiled cards used to craft it.
This creature has flying as long as an exiled card used to craft it has flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, protection, reach, trample, and vigilance.

Altar of the Wretched

When this artifact enters, you may sacrifice a nontoken creature. If you do, draw X cards, then mill X cards, where X is that creature's power.
Craft with one or more creatures {2}{B}{B}
{2}{B}: Return this card from your graveyard to your hand.

Altar of the Wretched // Wretched Bonemass

Cinderbones

Wither (This deals damage to creatures in the form of -1/-1 counters.)
{1}{B}: Regenerate this creature.

Ajani Fells the Godsire

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Exile target creature an opponent controls with power 3 or greater.
II — Create a 2/1 white Cat Warrior creature token, then put a vigilance counter on a creature you control.
III — Target creature you control gains double strike until end of turn.

Accursed Centaur

When this creature enters, sacrifice a creature.

Debtors' Transport

Afterlife 2 (When this creature dies, create two 1/1 white and black Spirit creature tokens with flying.)

Aerie Ouphes

Sacrifice this creature: It deals damage equal to its power to target creature with flying.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Cloudthresher

Flash
Reach
When this creature enters, it deals 2 damage to each creature with flying and each player.
Evoke {2}{G}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Augur of Skulls

{1}{B}: Regenerate this creature.
Sacrifice this creature: Target player discards two cards. Activate only during your upkeep.

Butcher Ghoul

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Champion of Stray Souls

{3}{B}{B}, {T}, Sacrifice X other creatures: Return X target creature cards from your graveyard to the battlefield.
{5}{B}{B}: Put this card from your graveyard on top of your library.

Forest

Beledros Witherbloom

Flying
At the beginning of each upkeep, create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."
Pay 10 life: Untap all lands you control. Activate only once each turn.

Pull from Eternity

Put target face-up exiled card into its owner's graveyard.

Clattering Skeletons

When this creature dies, venture into the dungeon. (Enter the first room or advance to the next room.)

Underworld Sentinel

Whenever this creature attacks, exile target creature card from your graveyard.
When this creature dies, put all cards exiled with it onto the battlefield.

Deathless Knight

Haste
When you gain life for the first time each turn, return this card from your graveyard to your hand.

All Is Dust

Each player sacrifices all permanents they control that are one or more colors.

Dimir House Guard

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Sacrifice a creature: Regenerate this creature.
Transmute {1}{B}{B} ({1}{B}{B}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Caldaia Strongarm

When this creature enters, put two +1/+1 counters on target creature.
Blitz {3}{G} (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)

Gutterbones

This creature enters tapped.
{1}{B}: Return this card from your graveyard to your hand. Activate only during your turn and only if an opponent lost life this turn.

Meadowboon

When this creature leaves the battlefield, put a +1/+1 counter on each creature target player controls.
Evoke {3}{W} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Accursed Marauder

When this creature enters, each player sacrifices a nontoken creature of their choice.

Walker of the Grove

When this creature leaves the battlefield, create a 4/4 green Elemental creature token.
Evoke {4}{G} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Altar of Bone

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a creature card, reveal it, put it into your hand, then shuffle.

Bone Dragon

Flying
{3}{B}{B}, Exile seven other cards from your graveyard: Return this card from your graveyard to the battlefield tapped.

Agency Coroner

{2}{B}, Sacrifice another creature: Draw a card. If the sacrificed creature was suspected, draw two cards instead.

Manor Skeleton

Marrow Bats

Flying
Pay 4 life: Regenerate this creature.

Tinybones, the Pickpocket

Deathtouch
Whenever Tinybones deals combat damage to a player, you may cast target nonland permanent card from that player's graveyard, and mana of any type can be spent to cast that spell.

Ajani's Last Stand

Whenever a creature or planeswalker you control dies, you may sacrifice this enchantment. If you do, create a 4/4 white Avatar creature token with flying.
When a spell or ability an opponent controls causes you to discard this card, if you control a Plains, create a 4/4 white Avatar creature token with flying.

Asphodel Wanderer

Acolyte of Aclazotz

{T}, Sacrifice another creature or artifact: Each opponent loses 1 life and you gain 1 life.

Myrkul, Lord of Bones

As long as your life total is less than or equal to half your starting life total, Myrkul has indestructible.
Whenever another nontoken creature you control dies, you may exile it. If you do, create a token that's a copy of that card, except it's an enchantment and loses all other card types.

Marang River Skeleton

{B}: Regenerate this creature.
Megamorph {3}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)

Abzan Advantage

Target player sacrifices an enchantment of their choice. Bolster 1. (Choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.)

Moss-Pit Skeleton

Kicker {3} (You may pay an additional {3} as you cast this spell.)
If this creature was kicked, it enters with three +1/+1 counters on it.
Whenever one or more +1/+1 counters are put on a creature you control, if this card is in your graveyard, you may put this card on top of your library.

Skeleton Crew

Each other creature you control that's a Skeleton or Pirate gets +1/+1.
Whenever one or more creature cards leave your graveyard, create a 2/2 black Skeleton Pirate creature token. (This ability triggers only from the battlefield.)
{5}{B}: Return this card from your graveyard to the battlefield tapped.

Ajani's Aid

When this enchantment enters, you may search your library and/or graveyard for a card named Ajani, Valiant Protector, reveal it, and put it into your hand. If you search your library this way, shuffle.
Sacrifice this enchantment: Prevent all combat damage a creature of your choice would deal this turn.

Mournwillow

Haste
Delirium — When this creature enters, if there are four or more card types among cards in your graveyard, creatures with power 2 or less can't block this turn.

Burr Grafter

Sacrifice this creature: Target creature gets +2/+2 until end of turn.
Soulshift 3 (When this creature dies, you may return target Spirit card with mana value 3 or less from your graveyard to your hand.)

Soul of Migration

Flying
When this creature enters, create two 1/1 white Bird creature tokens with flying.
Evoke {3}{W} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Golgari Grave-Troll

This creature enters with a +1/+1 counter on it for each creature card in your graveyard.
{1}, Remove a +1/+1 counter from this creature: Regenerate this creature.
Dredge 6 (If you would draw a card, you may mill six cards instead. If you do, return this card from your graveyard to your hand.)