Nightmare

Whenever this creature attacks or blocks, each opponent exiles the top two cards of their library.

Tendrils of Corruption

Tendrils of Corruption deals X damage to target creature and you gain X life, where X is the number of Swamps you control.

Enormous Baloth

Naturalize

Assassinate

Warpath Ghoul

Bog Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Doom Blade

Giant Growth

Target creature gets +3/+3 until end of turn.

Cemetery Reaper

Other Zombie creatures you control get +1/+1.
{2}{B}, {T}: Exile target creature card from a graveyard. Create a 2/2 black Zombie creature token.

Mind Rot

Consume Spirit

Spend only black mana on X.
Consume Spirit deals X damage to any target and you gain X life.

Forest

Howling Banshee

Flying
When Howling Banshee enters, each player loses 3 life.

Terramorphic Expanse

{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Drudge Skeletons

{B}: Regenerate Drudge Skeletons. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Zombie Goliath

Swamp

Rise from the Grave

Put target creature card from a graveyard onto the battlefield under your control. That creature is a black Zombie in addition to its other colors and types.

Gravedigger

When Gravedigger enters, you may return target creature card from your graveyard to your hand.

Wall of Bone

Defender (This creature can't attack.)
{B}: Regenerate Wall of Bone. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)