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

Flying, deathtouch

When Baleful Strix enters the battlefield, draw a card.

At the beginning of your end step, you may sacrifice an artifact, creature, enchantment, land, or planeswalker. If you do, each opponent may sacrifice a permanent that shares a card type with it. For each opponent who doesn't, that player loses 2 life and you draw a card.

Mentor (Whenever this creature attacks, put a +1/+1 counter on target attacking creature with lesser power.)

Creatures you control have "Whenever one or more counters are put on this creature for the first time each turn, draw a card."

Flying, first strike

Whenever Drana, Liberator of Malakir deals combat damage to a player, put a +1/+1 counter on each attacking creature you control.

{T}, Sacrifice a creature: Put two +1/+1 counters on target creature.

{T}, Remove a counter from a creature you control: Create a Treasure token.

{T}, Sacrifice an artifact: Create a 2/1 white and black Inkling creature token with flying.

{3}{B}: Untap Fain, the Broker.

Menace

Whenever another creature you control dies, put a +1/+1 counter on Feral Ghoul.

When Feral Ghoul dies, each opponent gets a number of rad counters equal to its power.

Whenever a creature enters the battlefield under your control this turn, put a +1/+1 counter on it and it gains haste until end of turn.

Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Morph {B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Whenever another nontoken creature you control dies, draw a card.

Hagra Constrictor enters the battlefield with two +1/+1 counters on it.

Each creature you control with a +1/+1 counter on it has menace. (A creature with menace can't be blocked except by two or more creatures.)

Creatures you control with +1/+1 counters on them can't be blocked.

Iron Apprentice enters the battlefield with a +1/+1 counter on it.

When Iron Apprentice dies, if it had counters on it, put those counters on target creature you control.

Whenever you sacrifice a permanent, put a +1/+1 counter on Juri, Master of the Revue.

When Juri dies, it deals damage equal to its power to any target.

At the beginning of your end step, you may sacrifice another creature. If you do, reveal cards from the top of your library until you reveal a nonlegendary creature card with lesser mana value, put it onto the battlefield, then put the rest on the bottom of your library in a random order.

At the beginning of your end step, create a Treasure token for each creature that died this turn. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)

Other creatures you control have dethrone.

Whenever a creature you control with a +1/+1 counter on it dies, return that card to the battlefield under your control at the beginning of the next end step.

Whenever Pyreheart Wolf attacks, creatures you control gain menace until end of turn. (They can't be blocked except by two or more creatures.)

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.)

Whenever River Kelpie or another permanent enters the battlefield from a graveyard, draw a card.

Whenever a player casts a spell from a graveyard, draw a card.

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.)

{1}{B}, Sacrifice another creature: Put a +1/+1 counter on Skyclave Shadowcat.

Whenever a creature you control with a +1/+1 counter on it dies, draw a card.

When Solemn Simulacrum enters the battlefield, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

When Solemn Simulacrum dies, you may draw a card.

Flash

Thought Sponge enters the battlefield with a number of +1/+1 counters on it equal to the greatest number of cards an opponent has drawn this turn.

When Thought Sponge dies, draw cards equal to its power.

Whenever one or more artifact and/or creature cards leave your graveyard during your turn, put a +1/+1 counter on target creature you control.

Haste

Whenever Thundering Raiju attacks, put a +1/+1 counter on target creature you control. Then Thundering Raiju deals X damage to each opponent, where X is the number of modified creatures you control other than Thundering Raiju. (Equipment, Auras you control, and counters are modifications.)

Nontoken creatures you control have riot. (They enter the battlefield with your choice of a +1/+1 counter or haste.)

If a creature you control with a +1/+1 counter on it would deal damage to a permanent or player, it deals double that damage instead.

Target creature gains undying until end of turn. (When it 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.)

Pay 3 life: Put a +1/+1 counter on target creature.

Whenever Urborg Scavengers enters the battlefield or attacks, exile target card from a graveyard. Put a +1/+1 counter on Urborg Scavengers.

Urborg Scavengers has flying as long as a card exiled with it has flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, menace, reach, trample, and vigilance.

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.