msem-instigator

({T}: Add {W} or {U}.)
As Ruptured Square enters, you may pay {1}. If you don't, Ruptured Square enters tapped.

({T}: Add {R} or {G}.)
As Ruptured Trail enters, you may pay {1}. If you don't, Ruptured Trail enters tapped.

Target creature gets +2/+1 and gains trample until end of turn.

Target creature gets +3/+0 and gains first strike until end of turn.

Exile the top two cards of your library. Until the end of your next turn, you may play those cards. (If you cast a spell this way, you still pay its costs. You can play a land this way only if you have an available land play remaining.)

As an additional cost to cast this spell, put a card from your hand on the bottom of your library.
Draw two cards.

Gain control of target creature until end of turn. Untap that creature. Then create two 1/1 red Satyr creature tokens with “This creature can't block.” Creatures you control gain haste until end of turn.

Rushing Waters enters tapped.
{T}: Add {U} or {R}.
When Rushing Waters enters, you may put a loyalty counter on a planeswalker you control.

Flying
When Rushwater Hunter enters, you may return target creature to its owner's hand.

Improve {1}{U} ({1}{U}: Put a +1/+1 counter on this creature. This costs {1} more to activate for each +1/+1 counter on it. Improve only as a sorcery.)
At the beginning of your end step, if one or more embattled creatures you controlled dealt damage to a player, you may draw a card. (A creature is embattled if it has a counter on it or has a permanent you control attached to it.)

When Russet Denmother enters, choose one —
• Destroy target enchantment.
• Create a 2/1 red and white Fox creature token.

Rustshell Crustacean gets +1/+1 for each artifact you control.
Whenever Rustshell Crustacean attacks, choose one —
• Search your library for an Equipment card, reveal it, and put it into your hand, then shuffle.
• Create a Treasure token.

Whenever Rustshell Mantis is dealt damage, put that many +1/+1 counters on it. (It must survive the damage to get the counters.)

Deathtouch
Whenever Ruststep Centipede deals combat damage to a player, you may destroy target artifact or enchantment that player controls.

As an additional cost to cast this spell, sacrifice an artifact or creature.
Draw two cards.

Whenever you cast a spell from anywhere other than your hand, put a +1/+1 counter on Ruthless Advisor.
Surpass {5}{B} ({5}{B}: Transform this creature. This costs {1} less to activate for each counter on it. Activate only as a sorcery.)

Whenever you cast a spell from anywhere other than your hand, return Ruthless Bakhtak from your graveyard to your hand.

Target creature gains trample until end of turn. The next time a source of your choice would deal damage to that creature, prevent that damage. If damage is prevented this way, that creature gets +X/+0 until end of turn, where X is the amount of damage prevented this way.

First strike
Ruthless Blademaster gets +1/+0 for each Equipment attached to it.

Whenever another creature with power 4 or greater you control attacks, Ruthless Brawler deals 1 damage to defending player.

When Ruthless Conscript dies, arm up to two target creatures you control. (Create a colorless Equipment artifact token with “Equipped creature gets +1/+0” and equip {2}, then attach it to that creature.)

Whenever you cast a spell that's red, green, white, or blue, each opponent loses 1 life and you gain 1 life.

{2}{R}: Ruthless Mastiff gets +3/+0 until end of turn.

{2}, Remove a counter from another permanent you control: Ruthless Monstrosity gets +2/+2 until end of turn.

Alpha (You may have this creature enter with a +1/+1 counter on it. If you do, it becomes alpha and can only attack alone.)
Ruthless Predator can't be blocked by more than one creature.