Counterspell

Orvar, the All-Form

Changeling
Whenever you cast an instant or sorcery spell, if it targets one or more other permanents you control, create a token that's a copy of one of those permanents.
When a spell or ability an opponent controls causes you to discard this card, create a token that's a copy of target permanent.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Whelming Wave

Return all creatures to their owners' hands except for Krakens, Leviathans, Octopuses, and Serpents.

Enervate

Tap target artifact, creature, or land.
Draw a card at the beginning of the next turn's upkeep.

Intervene

Counter target spell that targets a creature.

Kiora, the Rising Tide

When Kiora enters, draw two cards, then discard two cards.
Threshold — Whenever Kiora attacks, if there are seven or more cards in your graveyard, you may create Scion of the Deep, a legendary 8/8 blue Octopus creature token.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Ichthyomorphosis

Enchant creature
Enchanted creature loses all abilities and is a blue Fish with base power and toughness 0/1.

Negate

Dispel

Charix, the Raging Isle

Spells your opponents cast that target Charix, the Raging Isle cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.