Don't Have

Rooftop Storm

You may pay {0} rather than pay the mana cost for Zombie creature spells you cast.

Rukarumel, Biologist

As Rukarumel, Biologist enters, choose a creature type.
Slivers you control and nontoken creatures you control are the chosen type in addition to their other creature types. The same is true for creature spells you control and creature cards you own that aren't on the battlefield.
{3}, {T}: Create a 1/1 colorless Sliver creature token.

Gravecrawler

Gravecrawler can't block.
You may cast Gravecrawler from your graveyard as long as you control a Zombie.

Necroduality

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