Mummy Paramount

Whenever another Zombie you control enters, Mummy Paramount gets +1/+1 until end of turn.

Plains

Corpse Knight

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

Ratadrabik of Urborg

Vigilance, ward {2}
Other Zombies you control have vigilance.
Whenever another legendary creature you control dies, create a token that's a copy of that creature, except it's not legendary and it's a 2/2 black Zombie in addition to its other colors and types.

Sparring Mummy

When Sparring Mummy enters, untap target creature.

Swamp

God-Eternal Oketra

Double strike
Whenever you cast a creature spell, create a 4/4 black Zombie Warrior creature token with vigilance.
When God-Eternal Oketra dies or is put into exile from the battlefield, you may put it into its owner's library third from the top.