Ordeal of Purphoros

Enchant creature
Whenever enchanted creature attacks, put a +1/+1 counter on it. Then if it has three or more +1/+1 counters on it, sacrifice Ordeal of Purphoros.
When you sacrifice Ordeal of Purphoros, it deals 3 damage to any target.

Omenspeaker

When Omenspeaker enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Lost in a Labyrinth

Target creature gets -3/-0 until end of turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Shipbreaker Kraken

{6}{U}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
When Shipbreaker Kraken becomes monstrous, tap up to four target creatures. Those creatures don't untap during their controllers' untap steps for as long as you control Shipbreaker Kraken.

Sealock Monster

Sealock Monster can't attack unless defending player controls an Island.
{5}{U}{U}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When Sealock Monster becomes monstrous, target land becomes an Island in addition to its other types.

Mountain

Magma Jet

Magma Jet deals 2 damage to any target. Scry 2.

Griptide

Put target creature on top of its owner's library.

Disperse

Return target nonland permanent to its owner's hand.

Island

Coral Merfolk

Stoneshock Giant

{6}{R}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When Stoneshock Giant becomes monstrous, creatures without flying your opponents control can't block this turn.

Wall of Frost

Defender
Whenever Wall of Frost blocks a creature, that creature doesn't untap during its controller's next untap step.

Sea God's Revenge

Return up to three target creatures your opponents control to their owners' hands. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Rage of Purphoros

Rage of Purphoros deals 4 damage to target creature. It can't be regenerated this turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Ill-Tempered Cyclops

Trample
{5}{R}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)

Burnished Hart

{3}, Sacrifice Burnished Hart: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.

Volcanic Geyser

Volcanic Geyser deals X damage to any target.

Lightning Strike

Lightning Strike deals 3 damage to any target.

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Water Servant

{U}: Water Servant gets +1/-1 until end of turn.
{U}: Water Servant gets -1/+1 until end of turn.

Shock

Crackling Triton

{2}{R}, Sacrifice Crackling Triton: It deals 2 damage to any target.

Dissolve

Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)