Wayward Servant

Whenever another Zombie you control enters, each opponent loses 1 life and you gain 1 life.

Sedraxis Alchemist

When Sedraxis Alchemist enters, if you control a blue permanent, return target nonland permanent to its owner's hand.

Rally the Ancestors

Return each creature card with mana value X or less from your graveyard to the battlefield. Exile those creatures at the beginning of your next upkeep. Exile Rally the Ancestors.

Necroduality

Whenever a nontoken Zombie you control enters, create a token that's a copy of that creature.

Counterspell

Corpse Knight

Whenever another creature you control enters, each opponent loses 1 life.