Into the Pit

You may look at the top card of your library any time.
You may cast spells from the top of your library by sacrificing a nonland permanent in addition to paying their other costs.

Ornithopter

Blood Artist

Whenever Blood Artist or another creature dies, target player loses 1 life and you gain 1 life.

Poxwalkers

Deathtouch
Curse of the Walking Pox — Whenever you cast a spell from anywhere other than your hand, return Poxwalkers from your graveyard to the battlefield tapped.

Priest of Gix

When Priest of Gix enters, add {B}{B}{B}.

Pitiless Plunderer

Whenever another creature you control dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Varragoth, Bloodsky Sire

Deathtouch
Boast — {1}{B}: Target player searches their library for a card, then shuffles and puts that card on top. (Activate only if this creature attacked this turn and only once each turn.)

Pawn of Ulamog

Whenever Pawn of Ulamog or another nontoken creature you control dies, you may create a 0/1 colorless Eldrazi Spawn creature token. It has "Sacrifice this creature: Add {C}."

Mortuary

Whenever a creature is put into your graveyard from the battlefield, put that card on top of your library.