Liesa, Shroud of Dusk

Rather than pay {2} for each previous time you've cast this spell from the command zone this game, pay 2 life that many times.
Flying, lifelink
Whenever a player casts a spell, they lose 2 life.

Agent of Masks

At the beginning of your upkeep, each opponent loses 1 life. You gain life equal to the life lost this way.

Agent of the Iron Throne

Commander creatures you own have "Whenever an artifact or creature you control is put into a graveyard from the battlefield, each opponent loses 1 life."

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.