Mana Leak

Counter target spell unless its controller pays {3}.

Deprive

As an additional cost to cast this spell, return a land you control to its owner's hand.
Counter target spell.

Frogify

Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Island

Disperse

Return target nonland permanent to its owner's hand.

Boomerang

Return target permanent to its owner's hand.

Rise from the Tides

Create a tapped 2/2 black Zombie creature token for each instant and sorcery card in your graveyard.

Sphinx of the Final Word

This spell can't be countered.
Flying
Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Instant and sorcery spells you control can't be countered.

Mystic Subdual

Flash
Enchant creature
Enchanted creature gets -2/-0 and loses all abilities. (Mutating onto the creature won't give it new abilities. It can gain abilities in other ways.)

Voracious Reader

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Instant and sorcery spells you cast cost {1} less to cast.

Curious Homunculus

{T}: Add {C}. Spend this mana only to cast an instant or sorcery spell.
At the beginning of your upkeep, if there are three or more instant and/or sorcery cards in your graveyard, transform this creature.

Curious Homunculus // Voracious Reader

Murmuring Mystic

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