Rabid Gnaw

Target creature you control gets +1/+0 until end of turn. Then it deals damage equal to its power to target creature you don't control.

Splash Portal

Exile target creature you control, then return it to the battlefield under its owner's control. If that creature is a Bird, Frog, Otter, or Rat, draw a card.

Alania, Divergent Storm

Whenever you cast a spell, if it's the first instant spell, the first sorcery spell, or the first Otter spell other than Alania you've cast this turn, you may have target opponent draw a card. If you do, copy that spell. You may choose new targets for the copy.

Waterspout Warden

Whenever Waterspout Warden attacks, if another creature entered the battlefield under your control this turn, Waterspout Warden gains flying until end of turn.

Mountain

Felonious Rage

Target creature you control gets +2/+0 and gains haste until end of turn. When that creature dies this turn, create a 2/2 white and blue Detective creature token.

Mind Spiral

Gift a tapped Fish (You may promise an opponent a gift as you cast this spell. If you do, they create a tapped 1/1 blue Fish creature token before its other effects.)
Target player draws three cards. If the gift was promised, tap target creature an opponent controls and put a stun counter on it. (If a permanent with a stun counter would become untapped, remove one from it instead.)

Charmed Sleep

Enchant creature
When Charmed Sleep enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Sword of Vengeance

Equipped creature gets +2/+0 and has first strike, vigilance, trample, and haste.
Equip {3}

Flame Lash

Mind Spring

Thieving Otter

Whenever Thieving Otter deals damage to an opponent, draw a card.

Coruscation Mage

Offspring {2} (You may pay an additional {2} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent.

Kindlespark Duo

{T}: Kindlespark Duo deals 1 damage to target opponent.
Whenever you cast a noncreature spell, untap Kindlespark Duo.

Alania's Pathmaker

When Alania's Pathmaker enters, exile the top card of your library. Until the end of your next turn, you may play that card.

Island

Bellowing Crier

When Bellowing Crier enters, draw a card, then discard a card.

Swiftwater Cliffs

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {R}.

Quaketusk Boar

Stormcatch Mentor

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Instant and sorcery spells you cast cost {1} less to cast.

Pearl of Wisdom

This spell costs {1} less to cast if you control an Otter.
Draw two cards.

Bria, Riptide Rogue

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Other creatures you control have prowess. (If a creature has multiple instances of prowess, each triggers separately.)
Whenever you cast a noncreature spell, target creature you control can't be blocked this turn.

Mockingbird

Flying
You may have Mockingbird enter as a copy of any creature on the battlefield with mana value less than or equal to the amount of mana spent to cast Mockingbird, except it's a Bird in addition to its other types and it has flying.