msem-instigator

When Realmwalker Domovoi enters, exile another target permanent you control. Return it to the battlefield under your control at the beginning of the next end step.

Reach
Whenever you cast a spell with mana value 5 or greater, Reaper Squad deals 3 damage to target player or planeswalker.

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

Enchant creature
Enchanted creature has deathtouch and “When this creature dies, create a 2/2 black Demon creature token.”
{1}{B}, Exile Reaping Mask from your graveyard: Create a 2/2 black Demon creature token.

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.

Reason Rots, Rage Remains deals X damage to any target.
Reconstruct {X}{R}{R} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

Gain control of target creature until end of turn. Untap that creature. It gains haste and defiance until end of turn. (Whenever that creature takes damage, if it survives and wasn't defiant, put a +1/+1 counter on it and it becomes defiant.)

(Activate each submodule once as a sorcery. When this enters, activate one submodule for free.)
{2}{B}: Reduce
You may sacrifice a nonland permanent. If you do, each opponent sacrifices a permanent that shares a type with it.
{2}{G}: Reuse
Return target permanent card from your graveyard to your hand.
{1}{B}{G}: Recycle
Rebirth Module gains “Once each turn, when you sacrifice a permanent, you may conjure a card named Data-Point into your hand.” (It's a sorcery that costs {2} with “Draw a card.”)

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

Whenever a nontoken creature with mana value 3 or less you control enters, exile it. If you do, create a token that's a copy of it, except it's a Construct creature instead of its other types.

Exile the top card of your library and up to one target permanent card from your graveyard. You may play cards exiled this way until the end of your next turn.
You may play an additional land this turn.

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.)

Return target instant or sorcery card from your graveyard to your hand.
Draw a card.

As an additional cost to cast this spell, sacrifice a creature.
Return two target creature cards from your graveyard to your hand.

Tap up to three target lands. They don't untap during their controller's next untap step.
Agonize (You may cast this card from your graveyard by putting a -1/-1 counter on a creature you control in addition to paying its other costs. Then exile this card.)

{T}, Sacrifice a land: Untap up to three target lands.

Haste
Whenever Reckless Dunerider attacks, if it's enchanted or equipped, you may draw a card. If you do, discard a card.

Trample
When Reckless Exemplar attacks, if its power is greater than its base power, target creature an opponent controls can't block this turn.

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.

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
When Reckless Guardian dies, create X 1/1 colorless Servo artifact creature tokens, where X is Reckless Guardian's power.