Mindstab Thrull

Whenever Mindstab Thrull attacks and isn't blocked, you may sacrifice it. If you do, defending player discards three cards.

Swamp

Thrull Retainer

Enchant creature
Enchanted creature gets +1/+1.
Sacrifice Thrull Retainer: Regenerate enchanted creature.

Thallid Devourer

At the beginning of your upkeep, put a spore counter on Thallid Devourer.
Remove three spore counters from Thallid Devourer: Create a 1/1 green Saproling creature token.
Sacrifice a Saproling: Thallid Devourer gets +1/+2 until end of turn.

Fungal Bloom

{G}{G}: Put a spore counter on target Fungus.

Breeding Pit

At the beginning of your upkeep, sacrifice Breeding Pit unless you pay {B}{B}.
At the beginning of your end step, create a 0/1 black Thrull creature token.

Initiates of the Ebon Hand

{1}: Add {B}. If this ability has been activated four or more times this turn, sacrifice Initiates of the Ebon Hand at the beginning of the next end step.

Forest

Hymn to Tourach

Target player discards two cards at random.

Thallid

At the beginning of your upkeep, put a spore counter on Thallid.
Remove three spore counters from Thallid: Create a 1/1 green Saproling creature token.

Elvish Farmer

At the beginning of your upkeep, put a spore counter on Elvish Farmer.
Remove three spore counters from Elvish Farmer: Create a 1/1 green Saproling creature token.
Sacrifice a Saproling: You gain 2 life.

Thelonite Monk

{T}, Sacrifice a green creature: Target land becomes a Forest. (This effect lasts indefinitely.)

Thelonite Druid

{1}{G}, {T}, Sacrifice a creature: Forests you control become 2/3 creatures until end of turn. They're still lands.

Hollow Trees

Hollow Trees enters the battlefield tapped.
You may choose not to untap Hollow Trees during your untap step.
At the beginning of your upkeep, if Hollow Trees is tapped, put a storage counter on it.
{T}, Remove any number of storage counters from Hollow Trees: Add {G} for each storage counter removed this way.