Mana Breach

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

Mystic Snake

Flash
When this creature enters, counter target spell.

Stenn, Paranoid Partisan

As Stenn enters, choose a card type other than creature or land.
Spells you cast of the chosen type cost {1} less to cast.
{1}{W}{U}: Exile Stenn. Return it to the battlefield under its owner's control at the beginning of the next end step.

Equilibrium

Whenever you cast a creature spell, you may pay {1}. If you do, return target creature to its owner's hand.

Frilled Mystic

Flash
When this creature enters, you may counter target spell.

Inga and Esika

Creatures you control have vigilance and "{T}: Add one mana of any color. Spend this mana only to cast a creature spell."
Whenever you cast a creature spell, if three or more mana from creatures was spent to cast it, draw a card.