msem-instigator

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

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

Menace

When Reha, Entropy's Call enters, you may search your library for any number of land cards with different names and exile them with harvest counters, then shuffle.
At the beginning of your upkeep, you may put a card that you own in exile with a harvest counter on it at random onto the battlefield tapped.

Whenever a creature dealt damage by Rei's Betrayer this turn dies, you gain life equal to that creature's toughness.

When Rei's Cultivator enters, create a green Aura enchantment token named Sowing Spring attached to target land. The token has enchant land, “Enchanted land's name is Flowering Expanse” and “Whenever enchanted land is tapped for mana, add one mana of any color.”

Reinbreaker Behemoth attacks each combat if able.

Harmony — Destroy target artifact or enchantment.
When Rejoicing Aristocrats enters, harmonize. (Trigger up to one harmony of one permanent you control.)

Trample, haste
When Rejuvenating Elemental enters, remove up to X -1/-1 counters from among creatures you control. Rejuvenating Elemental gets +1/+1 until end of turn for each counter removed this way.

When Relentless Toqui enters, put two +1/+1 counters on a creature you control.
Creatures you control with counters on them have haste and menace.

Vigilance
Whenever you cast an artifact spell, put a +1/+1 counter on Relitian Sentry.
Equipped creatures you control get +1/+1 and have first strike.

Trample, haste
When Relonche Cavalry enters, other creatures you control get +1/+0 and gain trample and haste until end of turn.

Remarkable Hunter must be blocked if able.

When Remembrance of Light enters, you may return target permanent card from your graveyard to your hand.
Revive—{4}{G}, Discard a card. ({4}{G}, Discard a card, Exile this card from your graveyard: Create a token that's a copy of it except it has no mana cost. Revive only as a sorcery.)

Renegade Spellweaver can't be blocked as long as you've foretold a card or cast a foretold spell this turn.

When Renili, Telenian Weaponist enters, you may exile another target creature until Renili leaves the battlefield.
When Renili leaves the battlefield, put a +1/+1 counter on each creature you control.

Flash
If a player would conjure a card, they instead conjure a card named Data-Point. (It's a sorcery that costs {2} with “Draw a card.”.)
If a player would copy a spell or cast a copy, they copy the card named Data-Point instead of anything else.

When Reprising Bard enters, exile target instant or sorcery card with mana value 3 or less from your graveyard. When Reprising Bard is no longer on the battlefield, copy the exiled card. You may cast the copy without paying its mana cost.

Lifelink
Whenever another creature you control with a counter on it dies, return it to its owner's hand. If that creature was an Avatar, return it to the battlefield under your control instead.

Flash
Whenever you cast a Tale, look at the top two cards of your library. Put one into your hand and the other back on top or into your graveyard.

Enspirit (As you cast this spell, you may exile a nonenchantment creature you control until this leaves the battlefield or fails to resolve. Reduce this spell's cost by the exiled card's mana value.)
When Returned Bokor dies, return it to its owner's hand.

At the beginning of your upkeep, if a library has twenty or fewer cards left in it, return Returned Explorer from your graveyard to the battlefield tapped.