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.

Walk the Aeons

Buyback—Sacrifice three Islands. (You may sacrifice three Islands in addition to any other costs as you cast this spell. If you do, put this card into your hand as it resolves.)
Target player takes an extra turn after this one.

Replication Technique

Demonstrate (When you cast this spell, you may copy it. If you do, choose an opponent to also copy it. Players may choose new targets for their copies.)
Create a token that's a copy of target permanent you control.

Thieving Otter

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

Storm-Kiln Artist

Storm-Kiln Artist gets +1/+0 for each artifact you control.
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a Treasure token.

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.

Kindlespark Duo

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

Confiscation Coup

Choose target artifact or creature. You get {E}{E}{E}{E} (four energy counters), then you may pay an amount of {E} equal to that permanent's mana value. If you do, gain control of it.

Commence the Endgame

This spell can't be countered.
Draw two cards, then amass Zombies X, where X is the number of cards in your hand. (Put X +1/+1 counters on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)

Karn's Temporal Sundering

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Target player takes an extra turn after this one. Return up to one target nonland permanent to its owner's hand. Exile Karn's Temporal Sundering.

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.

Tidings

Borrowing 100,000 Arrows

Draw a card for each tapped creature target opponent controls.

Circular Logic

Counter target spell unless its controller pays {1} for each card in your graveyard.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Lightshell Duo

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When this creature enters, surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Kitsa, Otterball Elite

Vigilance
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
{T}: Draw a card, then discard a card.
{2}, {T}: Copy target instant or sorcery spell you control. You may choose new targets for the copy. Activate only if Kitsa's power is 3 or greater.

Galvanic Iteration

When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
Flashback {1}{U}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

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, Frolicking Familiar gets +1/+1 until end of turn.

Frolicking Familiar // Blow Off Steam

Mana Geyser

Add {R} for each tapped land your opponents control.

Rapid Augmenter

Haste
Whenever another creature you control with base power 1 enters, it gains haste until end of turn.
Whenever another creature you control enters, if it wasn't cast, put a +1/+1 counter on Rapid Augmenter and Rapid Augmenter can't be blocked this turn.

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Tempest Angler

Whenever you cast a noncreature spell, put a +1/+1 counter on Tempest Angler.

Daring Waverider

When Daring Waverider 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.

Part the Waterveil

Take an extra turn after this one. Exile Part the Waterveil.
Awaken 6—{6}{U}{U}{U} (If you cast this spell for {6}{U}{U}{U}, also put six +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Boon of the Wish-Giver

Draw four cards.
Cycling {1} ({1}, Discard this card: Draw a card.)

Veyran, Voice of Duality

Magecraft — Whenever you cast or copy an instant or sorcery spell, Veyran, Voice of Duality gets +1/+1 until end of turn.
If you casting or copying an instant or sorcery spell causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Rousing Refrain

Add {R} for each card in target opponent's hand. Until end of turn, you don't lose this mana as steps and phases end. Exile Rousing Refrain with three time counters on it.
Suspend 3—{1}{R} (Rather than cast this card from your hand, you may pay {1}{R} and exile it with three time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Have

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.

Concentrate

Confound

Counter target spell that targets a creature.
Draw a card.

Seething Song

Mind Spring

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.

Temporal Manipulation

Stitch in Time

Flip a coin. If you win the flip, take an extra turn after this one.

Cancel

Thundertrap Trainer

Offspring {4} (You may pay an additional {4} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.)
When this creature enters, look at the top four cards of your library. You may reveal a noncreature, nonland card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Valley Floodcaller

Flash
You may cast noncreature spells as though they had flash.
Whenever you cast a noncreature spell, Birds, Frogs, Otters, and Rats you control get +1/+1 until end of turn. Untap them.

Eon Frolicker

Flying
When Eon Frolicker enters, if you cast it, target opponent takes an extra turn after this one. Until your next turn, you and planeswalkers you control gain protection from that player. (You and planeswalkers you control can't be targeted, dealt damage, or enchanted by anything controlled by that player.)

Clone Legion

For each creature target player controls, create a token that's a copy of that creature.

Bloodline Pretender

Changeling (This card is every creature type.)
As Bloodline Pretender enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on Bloodline Pretender.

Stormsplitter

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

Practical Research

Draw four cards. Then discard two cards unless you discard an instant or sorcery card.