msem-instigator

This spell costs {1} less to cast for each Desert you control.
When Crested Crustacean enters, return target permanent to its owner's hand.

Deep-Sea Terror can't attack unless seven or more cards are in your graveyard.

As an additional cost to cast this spell, you may tap
any number of untapped Angels and/or Nephilim you control. This spell costs {1} less to cast for each creature tapped this way.
Flying, vigilance
When Empyrean Scholar enters, each creature tapped to pay its additional cost becomes a 4/4 Angel creature with flying and vigilance. (This effect lasts indefinitely.)

Whenever a creature an opponent controls deals damage to you, monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)
Frigid Behemoth can't attack unless it's monstrous.

Defender
Civilized — As long as you control an artifact, a creature, and an enchantment, Hauling Hippopotamus can attack as though it didn't have defender.

Icecap Tortoise enters with three ice counters on it.
Icecap Tortoise has defender as long as it has an ice counter on it.
{1}{U}: Remove an ice counter from Icecap Tortoise.

Library Specter can't attack unless there are five or more noncreature, nonland cards in your graveyard.

This spell can't be countered.
Trample
Whenever Lumbering Thoctar becomes the target of a spell or ability, counter it. Then put a stun counter on Lumbering Thoctar.
Whenever Lumbering Thoctar becomes untapped, draw a card.

Flash
Oscanthor, Trader's Ruin can't be blocked.
Whenever a creature you control deals combat damage to a player, draw a card.

Return target permanent to its owner's hand.
Coalesce {7}{U} (You may cast this from your graveyard for {7}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

This spell can't be countered.
Flying, protection from cryptic
Whenever you cast a cryptic spell, cast a Sphinx spell, or draw a card, investigate.
{T}, Sacrifice ten Clues: You win the game.

This spell costs {1} less to cast for each enchantment you control.
Flying, lifelink, trample
Disturb {6}{B}{B}. That spell costs {1} less to cast for each enchantment you control. (You may cast this card from your graveyard transformed for its disturb cost.)

Indestructible
You may play cards from your graveyard.
If you would draw one or more cards, mill that many cards instead.
If a card would be put into your graveyard from anywhere other than your library, exile it instead.

Inspired — Whenever Bearer of Vile Incense becomes untapped, create a 0/1 black Cultist creature token with “{1}{B}{B}, Sacrifice three Cultists: Create a 5/5 black Demon creature token.”

Flying
Sacrifice six Swamps: Return Berbarus Unsealed from your graveyard to the battlefield with an indestructible counter on it. You draw six cards and you lose 6 life.

Bloodprice {4}{B} (You may cast this card by sacrificing a creature and paying its bloodprice.)
At the beginning of your upkeep, if there are five or more creature cards in your graveyard, create a 2/2 black Demon creature token.

This spell costs {2} less to cast for each creature that died this turn.
Flying, trample

{1}{B}, Sacrifice another creature: Draw a card and create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
{2}{B}, Sacrifice three Idols: Return Demon of Hubris from your graveyard to the battlefield. Activate only as a sorcery.

When Doomstep Giant enters, each player sacrifices a land.

This spell costs {1} less to cast for each card put into your graveyard from anywhere this turn.
At the beginning of each player's upkeep, that player loses 1 life, discards a card, and sacrifices a creature.

Flying, lifelink
Fallen Celestial can't block or be blocked by Angels, Demons, or Faeries.
At the beginning of each opponent's upkeep, that player loses 1 life and creates a 1/1 black Faerie creature token with flying.

Menace
Whenever Flayed Dunerazer attacks or blocks, sacrifice a permanent.

Lionize {2}{B} ({2}{B}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following abilities until end of turn. You may cast this card on a later turn from exile.)
Flying
Sacrifice a creature: Put a +1/+1 counter on this creature and tap it. Any player may activate this ability.

Bloodprice {B}{B}{B}{B} (You may cast this card by sacrificing a creature and paying its bloodprice.)
Lifelink, haste
Sacrifice another Demon: Jejun, Dark Hunter gains flying and indestructible until end of turn.

Flying, trample
At the beginning of combat on your turn, an opponent may sacrifice a creature. If they do, you may sacrifice a creature. If you do, repeat this process. If you don't, tap Kai'Jun.