Counterspell

Volcanic Island

Pirate Ship

Pirate Ship can't attack unless defending player controls an Island.
{T}: Pirate Ship deals 1 damage to any target.
When you control no Islands, sacrifice Pirate Ship.

Braingeyser

Lord of Atlantis

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

Clone

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

Island

Sol Ring

Prodigal Sorcerer

{T}: Prodigal Sorcerer deals 1 damage to any target.

Control Magic

Enchant creature
You control enchanted creature.

Disintegrate

Disintegrate deals X damage to any target. If it's a creature, it can't be regenerated this turn, and if it would die this turn, exile it instead.

Unsummon

Return target creature to its owner's hand.

Serendib Efreet

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

Stone Rain

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Shatter

Wheel of Fortune

Each player discards their hand, then draws seven cards.

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.

Mountain

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.