msem-instigator

If you have cast spells with mana payments of exactly {U} and exactly {R} this turn, you may cast this spell without paying its mana cost and as though it has flash.
Whenever you cast an instant or sorcery spell with mana value 1 for the first time each turn, copy it. You may choose new targets for the copy.

When Political Opportunist enters, you may shuffle the cards from your hand into your library, then draw that many cards.

When Press-Gang Recruiter enters, create a Treasure token.
{5}, {T}, Sacrifice an artifact: Gain control of target artifact or creature until end of turn. Untap that permanent. It gains haste until end of turn. Activate only as a sorcery.

Once each turn, when one or more artifacts you control deals damage to an opponent, you may exile the top card of your library. You may play that card this turn. The same is true for enchantments, planeswalkers, instant spells, and sorcery spells.

If Professor Haldean would leave the battlefield, exile him instead.
Whenever you cast a spell, you may untap Professor Haldean and another target permanent.
{T}: Professor Haldean deals 1 damage to each opponent.

Qi-Long Shrine enters tapped.
{T}: Add {U} or {R}.
{U/R}, {T}, Sacrifice Qi-Long Shrine: Put a +1/+1 counter on target creature you control. Activate only as a sorcery.

You may have Raging Reflection enter as a copy of any creature on the battlefield, except it has “When this creature enters, it fights another target creature that shares a name with it.”

Each Merfolk and Wizard you control has “Whenever this creature attacks, abound.” (To abound, you may cast a spell that costs less than that creature from your hand without paying its mana cost.)

Exile the top three cards of your library. Until the end of your next turn, you may cast nonland cards exiled this way.
{3}{U}{R}: Return Reckless Experiment from your graveyard to the
battlefield tapped and transformed.

Each player exiles all permanents they control, draws that many cards, then puts up to that many permanent cards from their hand onto the battlefield. Exile Reform Reality.

Copy target instant or sorcery spell you control. You may choose new targets for the copy.(Cast a copy of this spell once while this creature is on the battlefield.)

Riga's Workshop enters tapped.
When Riga's Workshop enters, you may mill two cards.
{T}: Add {U} or {R}.

({T}: Add {U} or {R}.)
As Ritzy Parlor enters, you may pay {1}. If you don't, Ritzy Parlor enters tapped.

({T}: Add {U} or {R}.)
Roaring Cascade enters tapped.

Choose one —
• Return target instant or sorcery card from your graveyard to your hand.
• Return target exiled card with agonize you own to your hand.
Exile Romantic Recollections.

Rosegill Rover can't be blocked.
Whenever Rosegill Rover attacks, you may discard a card. If you do, draw a card.

Rousing Path enters tapped unless you control one or fewer other lands.
{T}: Add {U} or {R}.
Cycling {2} ({2}, Discard this card: Draw a card.)

({T}: Add {U} or {R}.)
As Ruptured Falls enters, you may pay {1}. If you don't, Ruptured Falls enters tapped.

Rushing Waters enters tapped.
{T}: Add {U} or {R}.
When Rushing Waters enters, you may put a loyalty counter on a planeswalker you control.

If you would draw your first card each turn, instead draw two cards, then discard a card.
Whenever you draw an even numbered card in a turn, put a +1/+1 counter on Saraf, Tuned Disciple. (The second, fourth, sixth, etc.)

When Sarrutu Worldbinder enters, create two 1/1 red Elemental creature tokens.
{1}{U}, {T}: Elementals you control gain flying until end of turn.
{2}{R}, {T}: Elementals you control get +2/+0 until end of turn.

Each instant and sorcery card in your graveyard has reprise. The reprise cost is equal to its mana cost. (As you cast an instant or sorcery spell, you may exile one card with reprise from your graveyard and pay its reprise cost. If you do, add its effects to that spell.)
Reprising spells you control can't be countered.

Prowess, haste
You may spend mana as though it were mana of any color to cast noncreature spells with mana value 3 or less.

Look at the top X cards of your library, where X is the number of instant and sorcery cards in your graveyard. You may reveal an instant or sorcery card from among them and put it on top of your library. Then put the rest on the bottom of your library in a random order.

Flying
Whenever an artifact you control enters, you may activate one of its activated abilities without paying its cost.