Pontiff of Blight

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Other creatures you control have extort. (If a creature has multiple instances of extort, each triggers separately.)

Curse of Fool's Wisdom

Enchant player
Whenever enchanted player draws a card, they lose 2 life and you gain 2 life.
Madness {3}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Aetherflux Reservoir

Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: This artifact deals 50 damage to any target.

Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Sanguine Bond

Whenever you gain life, target opponent loses that much life.

Swamp

Greed

Retreat to Hagra

Landfall — Whenever a land you control enters, choose one —
• Target creature gets +1/+0 and gains deathtouch until end of turn.
• Each opponent loses 1 life and you gain 1 life.

Polluted Bonds

Whenever a land an opponent controls enters, that player loses 2 life and you gain 2 life.

Dark Ritual

Prism Ring

As this artifact enters, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Revenge of Ravens

Whenever a creature attacks you or a planeswalker you control, that creature's controller loses 1 life and you gain 1 life.