Nether Void

Whenever a player casts a spell, counter it unless that player pays {3}.

Oppression

Whenever a player casts a spell, that player discards a card.

Mana Breach

Whenever a player casts a spell, that player returns a land they control to its owner's hand.

Oloro, Ageless Ascetic

At the beginning of your upkeep, you gain 2 life.
Whenever you gain life, you may pay {1}. If you do, draw a card and each opponent loses 1 life.
At the beginning of your upkeep, if Oloro is in the command zone, you gain 2 life.