Kormus Bell

All Swamps are 1/1 black creatures that are still lands.

Plague Mare

Plague Mare can't be blocked by white creatures.
When Plague Mare enters, creatures your opponents control get -1/-1 until end of turn.

Exterminatus

Nonland permanents your opponents control lose indestructible until end of turn.
Destroy all nonland permanents.

Dread of Night

Night Clubber

When Night Clubber enters, creatures your opponents control get -1/-1 until end of turn.
Blitz {2}{B} (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)

Nightcreep

Until end of turn, all creatures become black and all lands become Swamps.

Swamp

Suffocating Fumes

Creatures your opponents control get -1/-1 until end of turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

Zealous Persecution

Until end of turn, creatures you control get +1/+1 and creatures your opponents control get -1/-1.

Plains

Blanket of Night

Each land is a Swamp in addition to its other land types.

Contaminated Ground

Enchant land
Enchanted land is a Swamp.
Whenever enchanted land becomes tapped, its controller loses 2 life.

Ethereal Absolution

Creatures you control get +1/+1.
Creatures your opponents control get -1/-1.
{2}{W}{B}: Exile target card from an opponent's graveyard. If it was a creature card, you create a 1/1 white and black Spirit creature token with flying.