Lord of Atlantis

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

Counterspell

Azure Drake

Phantasmal Terrain

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

Energy Flux

All artifacts have "At the beginning of your upkeep, sacrifice this artifact unless you pay {2}."

Braingeyser

Power Sink

Counter target spell unless its controller pays {X}. If that player doesn't, they tap all lands with mana abilities they control and lose all unspent mana.

Island

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Aeolipile

{1}, {T}, Sacrifice Aeolipile: It deals 2 damage to any target.

Control Magic

Enchant creature
You control enchanted creature.

Serendib Efreet

Flying
At the beginning of your upkeep, Serendib Efreet deals 1 damage to you.

Psionic Blast

Psionic Blast deals 4 damage to any target and 2 damage to you.

Strip Mine

{T}: Add {C}.
{T}, Sacrifice Strip Mine: Destroy target land.

Psychic Purge

Psychic Purge deals 1 damage to any target.
When a spell or ability an opponent controls causes you to discard Psychic Purge, that player loses 5 life.

River Merfolk

{U}: River Merfolk gains mountainwalk until end of turn. (It can't be blocked as long as defending player controls a Mountain.)

Boomerang

Return target permanent to its owner's hand.

Mishra's Factory

{T}: Add {C}.
{1}: Mishra's Factory becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.