Howl from Beyond

Target creature gets +X/+0 until end of turn.

Doubling Season

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.
If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

Ravenous Squirrel

Whenever you sacrifice an artifact or creature, put a +1/+1 counter on Ravenous Squirrel.
{1}{B}{G}, Sacrifice an artifact or creature: You gain 1 life and draw a card.

Mirkwood Bats

Flying
Whenever you create or sacrifice a token, each opponent loses 1 life.

Symbiotic Beast

When Symbiotic Beast dies, create four 1/1 green Insect creature tokens.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature of their choice.

Fake Your Own Death

Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield tapped under its owner's control and you create a Treasure token." (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Infestation Sage

When this creature dies, create a 1/1 black and green Insect creature token with flying.

Preposterous Proportions

Creatures you control get +10/+10 and gain vigilance until end of turn.

Prossh, Skyraider of Kher

When you cast this spell, create X 0/1 red Kobold creature tokens named Kobolds of Kher Keep, where X is the amount of mana spent to cast it.
Flying
Sacrifice another creature: Prossh, Skyraider of Kher gets +1/+0 until end of turn.

Goblin Anarchomancer

Each spell you cast that's red or green costs {1} less to cast.

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Chandra, Flameshaper

+2: Add {R}{R}{R}. Exile the top three cards of your library. Choose one. You may play that card this turn.
+1: Create a token that's a copy of target creature you control, except it has haste and "At the beginning of the end step, sacrifice this token."
−4: Chandra deals 8 damage divided as you choose among any number of target creatures and/or planeswalkers.

Liliana, Dreadhorde General

Whenever a creature you control dies, draw a card.
+1: Create a 2/2 black Zombie creature token.
−4: Each player sacrifices two creatures of their choice.
−9: Each opponent chooses a permanent they control of each permanent type and sacrifices the rest.

Vengeful Bloodwitch

Whenever this creature or another creature you control dies, target opponent loses 1 life and you gain 1 life.