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.

Hunt for Specimens

Create a 1/1 black and green Pest creature token with "When this token dies, you gain 1 life."
Learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Consuming Corruption

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

Endless Atlas

{2}, {T}: Draw a card. Activate only if you control three or more lands with the same name.

Mutilate

All creatures get -1/-1 until end of turn for each Swamp you control.

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.

Swamp

Wall of Souls

Defender (This creature can't attack.)
Whenever this creature is dealt combat damage, it deals that much damage to target opponent or planeswalker.

Defile

Target creature gets -1/-1 until end of turn for each Swamp you control.

Korlash, Heir to Blackblade

Korlash's power and toughness are each equal to the number of Swamps you control.
{1}{B}: Regenerate Korlash.
Grandeur — Discard another card named Korlash, Heir to Blackblade: Search your library for up to two Swamp cards, put them onto the battlefield tapped, then shuffle.