Ebon Praetor

First strike, trample
At the beginning of your upkeep, put a -2/-2 counter on Ebon Praetor.
Sacrifice a creature: Remove a -2/-2 counter from Ebon Praetor. If the sacrificed creature was a Thrull, put a +1/+0 counter on Ebon Praetor. Activate only during your upkeep and only once each turn.

Dark Ritual

Thrull Surgeon

{1}{B}, Sacrifice Thrull Surgeon: Look at target player's hand and choose a card from it. That player discards that card. Activate only as a sorcery.

Basal Thrull

Soul Exchange

As an additional cost to cast this spell, exile a creature you control.
Return target creature card from your graveyard to the battlefield. Put a +2/+2 counter on that creature if the exiled creature was a Thrull.

Swamp

Thrull Champion

Thrull creatures get +1/+1.
{T}: Gain control of target Thrull for as long as you control Thrull Champion.

Armor Thrull

{T}, Sacrifice Armor Thrull: Put a +1/+2 counter on target creature.

Blood Pet

Mourning Thrull

({W/B} can be paid with either {W} or {B}.)
Flying
Whenever Mourning Thrull deals damage, you gain that much life.

Culling the Weak

As an additional cost to cast this spell, sacrifice a creature.
Add {B}{B}{B}{B}.

Death Pit Offering

When Death Pit Offering enters, sacrifice all creatures you control.
Creatures you control get +2/+2.

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.

Thrull Retainer

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

Endrek Sahr, Master Breeder

Whenever you cast a creature spell, create X 1/1 black Thrull creature tokens, where X is that spell's mana value.
When you control seven or more Thrulls, sacrifice Endrek Sahr, Master Breeder.