Altar of Dementia

Sacrifice a creature: Target player mills cards equal to the sacrificed creature's power.

Rooftop Storm

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

Dimir Signet

Sol Ring

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Gravecrawler

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

Grimgrin, Corpse-Born

Grimgrin, Corpse-Born enters tapped and doesn't untap during your untap step.
Sacrifice another creature: Untap Grimgrin and put a +1/+1 counter on it.
Whenever Grimgrin attacks, destroy target creature defending player controls, then put a +1/+1 counter on Grimgrin.

Necroduality

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