msem-instigator

Create two tokens that are copies of target creature you control, except the tokens aren't legendary if the creature is legendary. Those creatures gain haste until end of turn.

Flash
When Master of Disorientation enters, you may choose new targets for target instant or sorcery spell. Then proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

This spell can't be countered.
Flying, haste
Mayu, the Endless Flow gets +2/+2 for each spell you've cast this turn.

At the beginning of combat on your turn, if you cast an enchantment spell, an instant spell, and a sorcery spell this turn, create two 3/3 red Shark enchantment creature tokens. You may have any number of those tokens gain haste. If you do, sacrifice the tokens you chose at end of combat.

Reverberate {2}{U}{R} (When you cast this spell, copy it if you paid its reverberate cost. You may choose new targets for the copy.)
Exile target instant or sorcery card from your graveyard. You may cast a copy of that card without paying its mana cost.

Flash
Enchant instant or sorcery spell
Enchanted spell's text box is “This spell deals 3 damage to you.”
{4}{U}{U}{R}{R}: Return Mental Meltdown from your graveyard to the battlefield.

[+1]: Merkurio deals 2 damage to target player or planeswalker. That player or that planeswalker's controller may draw a card.
[–2]: The next instant or sorcery spell you cast this turn costs {U}{R} less to cast. This effect reduces only the amount of colored mana you pay.
[–7]: You get an emblem with “Each instant and sorcery card you own has reverberate {X}, where X is its mana value.” (When you cast a spell, copy it if you paid its reverberate cost. You may choose new targets for the copy.)

Kicker {2} (You may pay an additional {2} as you cast this spell.)
Prowess
When Merkurio's Opus enters, if it was kicked, draw two cards, then discard two cards.

[+1]: The next instant or sorcery spell you cast this turn costs {1} less to cast.
[–4]: Until end of turn, whenever you cast an instant or sorcery spell, Merkurio deals 2 damage to any target.
[–8]: Exile the top seven cards of your library. You may cast any number of instant and sorcery cards from among them without paying their mana costs.

Enchant creature
When Mesmerizing Shimmer enters, untap enchanted creature. It gains haste until end of turn.
You control enchanted creature.
Mirage {2}{U}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Each opponent discards all the cards in their hand, then draws that many cards. You discard your hand, then draw cards equal to the number of cards your opponents drew this turn.

Discard your hand, then draw three cards.
Mindstorm's Eye deals 3 damage to any target.

Flying, haste
Miyoga Firebird attacks each combat if able.
Whenever you cast your third instant or sorcery spell this turn, you may return Miyoga Firebird from your graveyard to the battlefield.

Haste
{1}: Exile Mizujutsu Master. Return it to the battlefield under its owner's control at the beginning of the next end step.

Prowess
Libraries can't be searched.
Spells you cast cost {1} less to cast for each permanent you control but don't own.

When Monastery Scribe enters, return target instant or sorcery card from your graveyard to your hand.

When Mountain-Western Inventor enters, you may return target artifact card from your graveyard to your hand.
{1}, Sacrifice an artifact: Target creature can't block or be blocked this turn.

Create a token that's a copy of target creature, except its power and toughness are switched. Sacrifice that token at the beginning of your next end step.

{1}, Discard a card: Create a Gold token. (It's an artifact with “Sacrifice this artifact: Add one mana of any color.”)
{T}, Sacrifice an artifact: Draw a card.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Nimble Elemental deals combat damage to a player, you may draw a card. If you do, discard a card.

Whenever you cast an instant or sorcery spell from your hand, you may cast target card with the same name as that spell from your graveyard. (You still pay its costs.)

When Ophidian Oracle enters, draw a card, then abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
Recite {2}{G}{G} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

Draw three cards, then discard two cards.

Whenever you cast a noncreature spell, creatures you control get +1/+1 until end of turn.

When Paint by Numbers enters, put up to ten brush counters on it.
Whenever a player casts a instant or sorcery spell with mana value equal to the number of brush counters on Paint by Numbers, remove a brush counter from it and copy that spell. You may choose new targets for the copy. Then sacrifice Paint by Numbers if it has no brush counters.