Mana Leak

Counter target spell unless its controller pays {3}.

Jace's Sanctum

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell, scry 1.

Counter target noncreature spell. Untap up to three lands.

Whenever you cast an instant or sorcery spell, create a 1/1 blue Bird Illusion creature token with flying.

Draw two cards, then discard two cards. Untap up to three lands.

Whenever you cast your first spell during each opponent's turn, draw a card.