msem-instigator

Equipped creature has “Whenever this creature attacks, untap each other creature you control.”
Equip {3}

Flying
When Rallywing enters, creatures you control get +1/+1 until end of turn.

Deception {2}{U}{U} ({2}{U}{U}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Whenever Raloran Insurgent deals combat damage to a player, abound. (You may cast a spell that costs less than this from your hand without paying its mana cost.)

Whenever Ram Wrangler attacks, until end of turn, gain control of target creature defending player controls with power less than or equal to the number of creatures in Ram Wrangler's pack. Tap it. It's attacking defending player. (Two or more creatures you control with equal power are in a pack.)

At the beginning of your end step, if a permanent you controlled left the battlefield this turn, put a party counter on Rambunctious Afterparty. Then Rambunctious Afterparty deals damage equal to the number of party counters on it to each opponent.

Whenever Rambunctious Upstart attacks, up to one target creature gets -3/-1 until end of turn and up to one target creature gets +3/+1 until end of turn.

Reach (This creature can block creatures with flying.)
Whenever a land you control enters, Rammanethi Sandshaper deals 1 damage to target creature with flying.

Flash
Voracious 2 (As this enters, you may sacrifice up to two artifacts and/or creatures. This creature enters with that many +1/+1 counters on it.)

Flash
Motivate 7 (When this creature enters, you may motivate target creature with less power than this by putting seven +1/+1 counters on it.)

When Rampaging Xiangshe 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 trample.

When this creature enters, for each kind of counter on target permanent, put another counter of that kind on it or remove one from it.

Equipped creature gets +2/+3 and has reach.
Equip Scout or Archer {1}
Equip {3}

Look at the top six cards of your library. Put up to one land card and up to two creature and/or planeswalker cards with total mana value 5 or less from among them onto the battlefield. Put the rest on the bottom of your library in a random order.

Enchant creature you control
When Rapacious Instinct enters, enchanted creature deals damage equal to its power to target creature you don't control.
Enchanted creature gets +1/+0.

First strike
When Rapacious Rattler enters, choose one or two targets you don't control. It deals 2 damage to the first and 1 damage to the second.

Flying
When Rapacious Regent enters, you may sacrifice another creature or artifact. If you do, Rapacious Regent deals 3 damage to any target.

Haste
Whenever Rapid Rodent attacks, it gets +1/+0 until end of turn for each other creature you control with flash and/or haste.

When Rat King enters, create two 1/1 black Rat creature tokens with “This creature can't block.”
Whenever Rat King or another creature you control dies, each opponent loses 1 life and you gain 1 life.

At the beginning of combat on your turn, choose a permanent type at random. Each player sacrifices a permanent of the chosen type other than this enchantment. If no permanents were sacrificed this way, sacrifice this enchantment and create a 6/6 black and red Rat Mutant creature token with trample and haste.

Whenever a creature you control dies, each opponent discards a card.
Revive {6}{B} ({6}{B}, 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.)

Whenever Ravaging Tyrant enters or attacks, each opponent loses 3 life, discards a card, and sacrifices a creature or planeswalker.

Reach, deathtouch
Whenever you cast a spell from your graveyard, you may have Raven-Cursed Dominik fight target creature.

Whenever Ravencaller or another creature enters from your graveyard, create a 1/1 blue Bird creature token with flying.

Whenever one or more other creatures you control deal combat damage to an opponent, choose one —
• That player discards a card at random.
• That player sacrifices a creature with toughness 4 or less.