As an additional cost to cast this spell, you may sacrifice any number of creatures. This spell costs less to cast for each creature sacrificed this way.
Each opponent sacrifices a creature of their choice. Create a 3/6 black and red Avatar creature token with haste and "Whenever this token attacks, it deals 3 damage to each opponent."

Flying
Whenever this creature enters or attacks, mill three cards.
Whenever one or more creature cards are put into your graveyard from your library, put one of them onto the battlefield.

Destroy target nonblack creature. It can't be regenerated. Create X 1/1 green Saproling creature tokens, where X is that creature's mana value.

Each opponent exiles cards from the top of their library until they exile a nonland card. You may cast any number of spells from among those nonland cards without paying their mana costs.
Rebound

Convoke
Vigilance

Affinity for artifacts
When Imskir enters, you draw X cards and you lose X life, where X is half the number of artifacts you control, rounded down.
, Sacrifice an artifact: Imskir deals damage equal to the sacrificed artifact's mana value to any target.

Magma Opus deals 4 damage divided as you choose among any number of targets. Tap two target permanents. Create a 4/4 blue and red Elemental creature token. Draw two cards.
, Discard this card: Create a Treasure token.

Convoke
Flying, lifelink, haste
Exalted
Other Vampires you control have exalted.

Treacherous Terrain deals damage to each opponent equal to the number of lands that player controls.
Basic landcycling

Assist (Another player can pay up to of this spell's cost.)
Flying
When this creature enters, return target instant, sorcery, or creature card from a graveyard to its owner's hand.

Flying
Whenever a creature dealt damage by this creature this turn dies, put a +1/+1 counter on this creature.
: This creature deals 1 damage to target creature.

Affinity for creatures
Flying, deathtouch
Instant and sorcery spells you cast have affinity for creatures.

When you cast this spell, you gain 1 life for each colorless permanent you control.
Hexproof from each color
Annihilator 2

You gain 2 life for each card in your graveyard, then shuffle your graveyard into your library.

Convoke
Flying

Affinity for creatures
Double strike

Flying
Morph
When this creature is turned face up, put two time counters on it and it gains vanishing. (At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.)

This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.
Morph

Delve
Draw three cards.

This spell costs less to cast for each Cave you control and each Cave card in your graveyard.
Lifelink

This spell costs less to cast for each creature card you own in exile and in your graveyard.
Menace, deathtouch

At the beginning of your upkeep, sacrifice two Swamps. If you can't, tap this creature, and an opponent may gain control of a creature you control of their choice for as long as this creature remains on the battlefield.
: Gain control of target creature for as long as this creature remains on the battlefield.

Delve
Deathtouch

: Regenerate this creature.

Open a sealed Magic booster pack, reveal the cards, and put all creature cards revealed this way onto the battlefield under your control. They're Zombies in addition to their other types. (Remove those cards from your deck before starting a new game.)

You control target player during that player's next turn. Exile Worst Fears. (You see all cards that player could see and make all decisions for the player.)

Menace, trample
Mayhem

When this creature dies, destroy all permanents at the beginning of the next end step.

Shuffle your library. As many times as you choose, you may exile the top card of your library. If the total mana value of the cards exiled this way is 13 or less, you may cast any number of spells from among those cards without paying their mana costs.