Combat Research

Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, draw a card."
As long as enchanted creature is legendary, it gets +1/+1 and has ward {1}. (Whenever enchanted creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)

Mountain

Pearl of Wisdom

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

Cryoshatter

Enchant creature
Enchanted creature gets -5/-0.
When enchanted creature becomes tapped or is dealt damage, destroy it.

Diminish

Target creature has base power and toughness 1/1 until end of turn.

Arcane Flight

Enchant creature
Enchanted creature gets +1/+1 and has flying.

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.

Island

Tempest Angler

Whenever you cast a noncreature spell, put a +1/+1 counter on this creature.

Brute Force

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

Stormsplitter

Haste
Whenever you cast an instant or sorcery spell, create a token that's a copy of this creature. Exile that token at the beginning of the next end step.

Daring Waverider

When this creature enters, you may cast target instant or sorcery card with mana value 4 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Channeled Dragonfire

Channeled Dragonfire deals 2 damage to any target.
Harmonize {5}{R}{R} (You may cast this card from your graveyard for its harmonize cost. You may tap a creature you control to reduce that cost by {X}, where X is its power. Then exile this spell.)

Spark of Creativity

Choose target creature. Exile the top card of your library. You may have Spark of Creativity deal damage to that creature equal to the exiled card's mana value. If you don't, you may play that card until end of turn.

Raze the Effigy

Choose one —
• Destroy target artifact.
• Target attacking creature gets +2/+2 until end of turn.

Convenient Target

Enchant creature
When this Aura enters, suspect enchanted creature. (It has menace and can't block.)
Enchanted creature gets +1/+1.
{2}{R}: Return this card from your graveyard to your hand.

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.

Blow Off Steam

Blow Off Steam deals 1 damage to any target. (Then exile this card. You may cast the creature later from exile.)

Frolicking Familiar

Flying
Whenever you cast an instant or sorcery spell, this creature gets +1/+1 until end of turn.

Frolicking Familiar // Blow Off Steam

Crimson Wisps

Target creature becomes red and gains haste until end of turn. (It can attack and {T} this turn.)
Draw a card.

Harnesser of Storms

Whenever you cast a noncreature or Otter spell, you may exile the top card of your library. Until end of turn, you may play that card. This ability triggers only once each turn.

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.

Alania's Pathmaker

When this creature enters, exile the top card of your library. Until the end of your next turn, you may play that card.

Negate

Thieving Otter

Whenever this creature deals damage to an opponent, draw a card.

Clout of the Dominus

Enchant creature
As long as enchanted creature is blue, it gets +1/+1 and has shroud. (It can't be the target of spells or abilities.)
As long as enchanted creature is red, it gets +1/+1 and has haste.

By Force

Lutri, the Spellchaser

Companion — Each nonland card in your starting deck has a different name. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
Flash
When Lutri enters, if you cast it, copy target instant or sorcery spell you control. You may choose new targets for the copy.