Prized Amalgam | Creature | Zombie | Whenever a creature enters the battlefield, if it entered from your graveyard or you cast it from your graveyard, return Prized Amalgam from your graveyard to the battlefield tapped at the beginning of the next end step. | Karl Kopinski
Olivia, Mobilized for War | Legendary Creature | Vampire Knight | Flying
Whenever another creature enters the battlefield under your control, you may discard a card. If you do, put a +1/+1 counter on that creature, it gains haste until end of turn, and it becomes a Vampire in addition to its other types. | Eric Deschamps
The Gitrog Monster | Legendary Creature | Frog Horror | Deathtouch
At the beginning of your upkeep, sacrifice The Gitrog Monster unless you sacrifice a land.
You may play an additional land on each of your turns.
Whenever one or more land cards are put into your graveyard from anywhere, draw a card. | Jason Kang