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.

Savra, Queen of the Golgari

Whenever you sacrifice a black creature, you may pay 2 life. If you do, each other player sacrifices a creature of their choice.
Whenever you sacrifice a green creature, you may gain 2 life.

Wardens of the Cycle

Morbid — At the beginning of your end step, if a creature died this turn, choose one —
• You gain 2 life.
• You draw a card and you lose 1 life.