Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters the battlefield, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue.

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Enchant creature
When Claustrophobia enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Draw three cards.

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Counter target creature spell.

You may cast Harbinger of the Tides as though it had flash if you pay more to cast it.
When Harbinger of the Tides enters the battlefield, you may return target tapped creature an opponent controls to its owner's hand.

Islandwalk
When Inkfathom Divers enters the battlefield, look at the top four cards of your library, then put them back in any order.

Other Merfolk creatures you control get +1/+1 and have islandwalk.

: Draw a card, then discard a card.

Other Merfolk creatures you control get +1/+1.
: Target Merfolk creature can't be blocked this turn.

Flying
When Merfolk Wayfinder enters the battlefield, reveal the top three cards of your library. Put all Island cards revealed this way into your hand and the rest on the bottom of your library in any order.

Other Merfolk creatures you control get +1/+1.
Whenever you cast a Merfolk spell, you may tap or untap target permanent.

Draw X cards.

You may exile a blue card from your hand rather than pay this spell's mana cost.
Change the target of target spell with a single target.

: Rootwater Hunter deals 1 damage to any target.

Whenever Scroll Thief deals combat damage to a player, draw a card.

: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn.
: Target land becomes an Island until end of turn.

When Tidal Courier enters the battlefield, reveal the top four cards of your library. Put all Merfolk cards revealed this way into your hand and the rest on the bottom of your library in any order.
: Tidal Courier gains flying until end of turn.

: Target land becomes an Island until end of turn.

Create a 5/5 blue Wall creature token with defender. Sacrifice it at the beginning of the next end step.

When Tidebinder Mage enters the battlefield, tap target red or green creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Tidebinder Mage.

Up to two target creatures each get +0/+3 until end of turn. Untap those creatures. At this turn's next end of combat, tap each creature that was blocked by one of those creatures this turn and it doesn't untap during its controller's next untap step.

Whenever a permanent you control becomes untapped, Wake Thrasher gets +1/+1 until end of turn.

Islandwalk
Whenever Cold-Eyed Selkie deals combat damage to a player, you may draw that many cards.

: Add .
, , Sacrifice Blighted Cataract: Draw two cards.

Lonely Sandbar enters the battlefield tapped.
: Add .
Cycling

Double strike
Whenever Warren Instigator deals damage to an opponent, you may put a Goblin creature card from your hand onto the battlefield.

Flying
Battle Squadron's power and toughness are each equal to the number of creatures you control.

Target creature gets +3/+1 and gains trample until end of turn.

Creatures you control gain double strike until end of turn.

, Sacrifice Ember Hauler: It deals 2 damage to any target.

Whenever another red creature enters the battlefield under your control, Foundry Street Denizen gets +1/+0 until end of turn.

Cycling
When you cycle Gempalm Incinerator, you may have it deal X damage to target creature, where X is the number of Goblins on the battlefield.

Ghostfire is colorless.
Ghostfire deals 3 damage to any target.

Haste
Other Goblin creatures you control get +1/+1 and have haste.

: Each creature attacks this turn if able.

Renown 1
As long as Goblin Glory Chaser is renowned, it has menace.

Goblin Goon can't attack unless you control more creatures than defending player.
Goblin Goon can't block unless you control more creatures than attacking player.

As an additional cost to cast this spell, sacrifice a Goblin.
Goblin Grenade deals 5 damage to any target.

Other Goblin creatures you control attack each combat if able.
At the beginning of combat on your turn, create a 1/1 red Goblin creature token with haste.
Whenever Goblin Rabblemaster attacks, it gets +1/+0 until end of turn for each other attacking Goblin.

, Sacrifice a land: Put a +1/+1 counter on Goblin Razerunners.
At the beginning of your end step, you may have Goblin Razerunners deal damage equal to the number of +1/+1 counters on it to target player or planeswalker.

Haste
When Goblin Ringleader enters the battlefield, reveal the top four cards of your library. Put all Goblin cards revealed this way into your hand and the rest on the bottom of your library in any order.

: Target creature with power 2 or less can't be blocked this turn.

Create three 1/1 red Goblin creature tokens.

: Create X 1/1 red Goblin creature tokens, where X is the number of Goblins you control.

Create two 1/1 red Goblin creature tokens.

Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase.

Tarfire deals 2 damage to any target.

, , Exile Brittle Effigy: Exile target creature.

, : Reveal cards from the top of your library until you reveal a land card. Goblin Charbelcher deals damage equal to the number of nonland cards revealed this way to any target. If the revealed land card was a Mountain, Goblin Charbelcher deals double that damage instead. Put the revealed cards on the bottom of your library in any order.

: Add .
, , Sacrifice Blighted Gorge: It deals 2 damage to any target.

Forgotten Cave enters the battlefield tapped.
: Add .
Cycling