msem-instigator

When Red-Crowned Admiral enters, create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Each creature you control with a +1/+1 counter on it has flying.

Other creatures you control get +0/+1.
{T}: Add {G}.

First strike
Redeye Commando's power is equal to twice the number of artifacts you control.
Redeye Commando attacks each turn if able.
Whenever Redeye Commando attacks, if its power is 6 or greater, it gains menace and trample until end of turn.

Redgill Corsair gets +1/+0 as long as you control an artifact.
When Redgill Corsair dies, create a Treasure token.

Redleather Armorer gets +1/+1 as long as it's your turn.

First strike
Whenever an opponent casts a noncreature spell, you gain 2 life.

Whenever you draw a card, put a hatch counter on Reefcrown Egg.
{T}, Sacrifice Reefcrown Egg: You may put a creature card with mana value less than or equal to the number of hatch counters on Reefcrown Egg from your hand onto the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Enchant creature
Enchanted creature gets +2/+2 for each other enchantment you control.

At the beginning of your upkeep, return target enchantment card from your graveyard to your hand.
Whenever Reflect on Serenity or another enchantment you control enters or leaves the battlefield, each opponent loses 1 life and you gain 1 life.

Each creature you control gets +1/+1 for each other creature you control with the same name.

Indestructible
When Reflected Worldwalker enters, each player puts their hand into their sideboard.

Flying
{2}{U}: Switch target creature's power and toughness until end of turn.

As Reflective Stalker enters, choose a noncreature card name.
When Reflective Stalker enters, if it was cast, create a token that's a copy of it.
Spells your opponents cast with the chosen name cost {2} more to cast.

Flying, lifelink

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
Shimmer (Whenever this creature attacks, create a tapped and attacking token that's a copy of it. Exile the token at the beginning of the next end step.)

When Refuse Trawler enters, you may pay {G}. If you do, choose one —
• Return a permanent card from your graveyard to your hand.
• Rediscover a permanent card. (Look at the top card of your library. You may reveal it and put it into your hand if it's a permanent card. Otherwise, put it back or into your graveyard.)

First strike, trample
Whenever Regal Coralhorn deals combat damage to a player or planeswalker, return target card with a cycling ability from your graveyard to your hand.
Cycling {2} ({2}, Discard this card: Draw a card.)

Menace
Regal Dragoon gets +1/+1 as long as you control a legendary creature.

Slipstream (This creature can't be blocked as long as only creatures with slipstream are attacking.)
As long as you control three or more artifacts, Regal Seasnake has vigilance. (Attacking doesn't cause it to tap.)

Whenever Regretful Chronicler is dealt damage, put a +1/+1 counter on it. (It must survive the damage to get the counter.)
Surpass {5}{U} ({5}{U}: Transform this. This
costs 1 less to activate for each counter on it. Activate only as a sorcery.)

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell, Regrets of Mortals gets +2/+0 until end of turn. You may discard a card. If you do, draw a card.

Legacy (You may play this side of this card only from your graveyard. Exile it if it would leave the battlefield or not resolve.)
At the beginning of your upkeep, you may return a creature card from your graveyard to your hand. If you do, you gain 2 life.

Menace

At the beginning of combat on your turn, you may have Regurgitator Ooze consume. If you do, it gets +2/+2 until end of turn. (To consume, sacrifice another creature or exile a creature card from your graveyard.)
When Regurgitator Ooze dies, return a card exiled with it to its owner's hand.