Dina, Soul Steeper

Whenever you gain life, each opponent loses 1 life.
{1}, Sacrifice another creature: Dina, Soul Steeper gets +X/+0 until end of turn, where X is the sacrificed creature's power.

Sanguine Bond

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

Exquisite Blood

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

Witherbloom Pledgemage

Magecraft — Whenever you cast or copy an instant or sorcery spell, you gain 1 life.

Chain of Smog

Target player discards two cards. That player may copy this spell and may choose a new target for that copy.

Witherbloom Apprentice

Magecraft — Whenever you cast or copy an instant or sorcery spell, each opponent loses 1 life and you gain 1 life.