Gangrenous Zombies

{T}, Sacrifice this creature: This creature deals 1 damage to each creature and each player. If you control a snow Swamp, this creature deals 2 damage to each creature and each player instead.

Headless Rider

Whenever this creature or another nontoken Zombie you control dies, create a 2/2 black Zombie creature token.

Archghoul of Thraben

Whenever this creature or another Zombie you control dies, look at the top card of your library. If it's a Zombie card, you may reveal it and put it into your hand. If you don't put the card into your hand, you may put it into your graveyard.