Compulsive Research

Target player draws three cards. Then that player discards two cards unless they discard a land card.

Ravenous Rats

When Ravenous Rats enters the battlefield, target opponent discards a card.

Island

Swamp

Diabolic Edict

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.

Chittering Rats

When Chittering Rats enters the battlefield, target opponent puts a card from their hand on top of their library.

Mulldrifter

Flying
When Mulldrifter enters the battlefield, draw two cards.
Evoke {2}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters the battlefield.)

Corrupt

Corrupt deals damage to any target equal to the number of Swamps you control. You gain life equal to the damage dealt this way.

Innocent Blood

Terramorphic Expanse

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

Grim Harvest

Return target creature card from your graveyard to your hand.
Recover {2}{B} (When a creature is put into your graveyard from the battlefield, you may pay {2}{B}. If you do, return this card from your graveyard to your hand. Otherwise, exile this card.)

Deep Analysis

Target player draws two cards.
Flashback—{1}{U}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Crypt Rats

{X}: Crypt Rats deals X damage to each creature and each player. Spend only black mana on X.