msem-instigator

Whenever a Plains you control enters, you may put a creature card with mana value 2 or less from your hand onto the battlefield.

You may have Reaping Willow assign its combat damage as though it weren't blocked.
{2}{G}: Reaping Willow gains indestructible until end of turn.

As Reborn Altar enters, you may pay 3 life. If you don't, it enters tapped.
{T}: Add {R}, {W}, or {B}.

Rediscover an artifact card, then do the same for creature, enchantment, instant, land, planeswalker, and sorcery. (Each time, look at the top card of your library. You may reveal it and put it into your hand if it's of that type. Otherwise, put it back or into your graveyard.)

Counter target spell unless its controller pays {1}. If they do, draw a card.

Exile target instant or sorcery spell you control. Until end of turn, you may cast that card from exile without paying its mana cost. When you do, copy it. You may choose new targets for the copy.

Draw two cards. You may play an additional land this turn.
Coalesce {5}{G}{U} (You may cast this from your graveyard for {5}{G}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

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.

Starting with you, each player either passes or reveals the top card of their library. Each player that revealed a card this way pays life equal to its mana value. If a player can't, that player passes. Then each player who hasn't passed yet puts that card into their hand. Repeat this process until each player has passed.

{T}: Target creature gains haste until end of turn.
{1}{R}, {T}, Sacrifice a Human: Create a token that's a copy of the sacrificed creature, except it's a 3/2 colorless Horror. It gains haste until end of turn. Activate only as a sorcery.

Whenever you cast a noncreature spell, you may put a progress counter on Reckless Research.
[progress 2+] At the beginning of your end step, mill two cards.
[progress 7+] At the beginning of your upkeep, choose target instant or sorcery card in your graveyard. You may cast it from your graveyard this turn.
At the beginning of your upkeep, choose target instant or sorcery card in your graveyard. You may cast it from your graveyard this turn.

Trial 6 (As you cast this spell, an opponent of your choice may pay 6 life. If they don't, they fail the trial.)
Flying
When Reckoner of Man enters, if the trial was failed, it deals 3 damage to each creature you don't control.

Whenever Reclamation Grovesculptor enters or attacks, put a growth counter on target noncreature permanent. It becomes a colorless Forest land and loses all other card types and land types.

Whenever a creature you control deals combat damage to an opponent or planeswalker, put a technology counter on Reclamation Project.
Remove X technology counters from Reclamation Project: You may cast target artifact or creature card with mana value X from your graveyard this turn. That creature enters as an artifact in addition to its other types. X can't be 0.

When Reclamation Sage enters, you may destroy target artifact or enchantment.

Flash
{U}, Return another creature you control to its owner's hand: Reclusive Archmage can't be blocked this turn and gains hexproof until end of turn. Activate only once each turn.

Reclusive Copse enters tapped.
{T}: Add {B} or {G}.
{1}{B}{G}: Until end of turn, Reclusive Copse becomes an Insect creature with deathtouch in addition to its other types.
Scavenge {B}{G}

When Recognification Process enters and at the beginning of your upkeep, create a token that's a copy of target artifact you control, then sacrifice an artifact.

Menace
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Return target artifact, enchantment, or planeswalker card with mana value 3 or less from your graveyard to the battlefield.

Choose one —
• Counter target spell unless its controller pays {2}.
• Draw a card.

Destroy target noncreature permanent. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Flash
Prowess
When Reconstructed Adept enters, target instant or sorcery card in your graveyard gains agonize until end of turn. (You may cast it by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile that card.)

Flying, lifelink
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Recreator of Myths attacks, you may cast target instant or sorcery spell from your graveyard. If you do, exile that card instead of putting it into your graveyard as it resolves.

Whenever Recurring Abomination deals combat damage to an opponent, you may put target creature card with mana value 3 or less from a graveyard onto the battlefield under your control.
{4}{B}{B}: Return Recurring Abomination from your graveyard to the battlefield tapped.