msem-instigator

Menace
When Rattled Bones dies, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)

First strike, trample
Whenever a creature dealt combat damage by Ravenous Forsaken this turn dies, put a +1/+1 counter on Ravenous Forsaken.
{2}{R}: Ravenous Forsaken gets +3/+0 until end of turn.

Ravenous Hollow enters tapped.
{T}: Add {B} or {R}.
{2}{B}{R}: Until end of turn, Ravenous Hollow becomes a Wolf creature with first strike in addition to its other types.
Scavenge {2}{B}{R}

When Ravenous Rats enters, target opponent discards a card.

Whenever a Survivor you control enters, you may draw a card. If you do, discard a card.

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.

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

This creature gets +1/+1 for each creature card in your graveyard.
{4}{R}, Sacrifice another creature: Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. Activate only as a sorcery.

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

{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.

Lionize {1}{B} ({1}{B}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following abilities until end of turn. You may cast this card on a later turn from exile.)
Flying, lifelink
Whenever this creature deals combat damage to a player, remove all counters from target permanent they control or protect.

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

{2}{B}{B}, Exile Reclusive Augur from your graveyard: Return another target creature card from your graveyard to the battlefield. Activate only during your turn.

When Recon Drone enters, you may search your library for a basic land card, reveal it, put it into your hand, then shuffle. Then if you did, put a card from your hand on the bottom of your library.

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

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

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.)

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

Menace

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.”

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.

Relic Hoarder gets +1/+0 for each artifact and/or enchantment you control.
Relic Hoarder has first strike as long as you control three or more artifacts and/or enchantments.