Merfolk of the Pearl Trident

Black Vise

As this artifact enters, choose an opponent.
At the beginning of the chosen player's upkeep, this artifact deals X damage to that player, where X is the number of cards in their hand minus 4.

Lord of Atlantis

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

Mox Sapphire

Braingeyser

Ancestral Recall

Prevent all combat damage that would be dealt this turn.

Unsummon

Return target creature to its owner's hand.

Counterspell

Mana Short

Tap all lands target player controls and that player loses all unspent mana.

Mox Emerald

Black Lotus

{T}, Sacrifice this artifact: Add three mana of any one color.

Giant Growth

Target creature gets +3/+3 until end of turn.

Tropical Island

Channel

Until end of turn, any time you could activate a mana ability, you may pay 1 life. If you do, add {C}.