Counterspell

Sol Ring

Phantasmal Terrain

Enchant land
As Phantasmal Terrain enters, choose a basic land type.
Enchanted land is the chosen type.

Clone

You may have Clone enter as a copy of any creature on the battlefield.

Island

Lord of Atlantis

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Merfolk of the Pearl Trident

Unstable Mutation

Enchant creature
Enchanted creature gets +3/+3.
At the beginning of the upkeep of enchanted creature's controller, put a -1/-1 counter on that creature.

Unsummon

Return target creature to its owner's hand.

Control Magic

Enchant creature
You control enchanted creature.

Mahamoti Djinn

Flying (This creature can't be blocked except by creatures with flying or reach.)