Sacrifice a creature: Add {C}{C}.

At the beginning of each upkeep, untap all creatures and lands.

Whenever you cast a creature spell, draw a card.

Whenever you draw a card, put a +1/+1 counter on Chasm Skulker.

When Chasm Skulker dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on Chasm Skulker. (They can't be blocked as long as defending player controls an Island.)

As Cloud Key enters the battlefield, choose artifact, creature, enchantment, instant, or sorcery.

Spells you cast of the chosen type cost {1} less to cast.

As an additional cost to cast this spell, sacrifice a creature.

Search your library for a card, put that card into your hand, then shuffle.

Flash

Whenever a creature you control dies, each opponent sacrifices a creature.

Put any number of target creature cards from your graveyard on top of your library.

Draw a card.

Put any number of target creature cards from your graveyard on top of your library.

Draw a card.

Put any number of target creature cards from your graveyard on top of your library.

Draw a card.

Face-down creatures get +1/+1.

{2}{U}: Turn target face-down creature face up.

If you would draw a card while your library has no cards in it, you win the game instead.

+1: Target player mills two cards. Draw a card.

-8: Draw seven cards. Then if your library has no cards in it, you win the game.

The first face-down creature spell you cast each turn costs {3} less to cast.

Whenever a face-down creature enters the battlefield under your control, draw a card.

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.

You may cast spells as though they had flash.

You may look at the top card of your library any time.

You may cast artifact spells and colorless spells from the top of your library.

{T}, Pay 1 life: Exile the top card of your library.

Face-down creature spells you cast cost {1} less to cast.

{1}{G}: Turn Obscuring Aether face down. (It becomes a 2/2 creature.)

Trample

Whenever a source deals damage to Phyrexian Obliterator, that source's controller sacrifices that many permanents.

Psychosis Crawler's power and toughness are each equal to the number of cards in your hand.

Whenever you draw a card, each opponent loses 1 life.

Untap all permanents you control during each other player's untap step.

When Thassa's Oracle enters the battlefield, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Colorless spells you cast cost {2} less to cast.

+1: Exile the top card of your library face down and look at it. Create a 2/2 colorless Spirit creature token. When that token leaves the battlefield, put the exiled card into your hand.

-3: Destroy target permanent that's one or more colors.

Sacrifice a creature: Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

You may cast creature spells as though they had flash.

+1: Until your next turn, up to one target creature gains vigilance and reach.

-2: Look at the top three cards of your library. Exile one face down and put the rest on the bottom of your library in any order. For as long as it remains exiled, you may look at that card and you may cast it if it's a creature spell.

You may look at the top card of your library any time.

You may cast creature spells from the top of your library.

You may spend mana as though it were mana of any type to cast creature spells.

Haste

Whenever a creature an opponent controls dies, put a +1/+1 counter on Yahenni, Undying Partisan.

Sacrifice another creature: Yahenni gains indestructible until end of turn.