msem-instigator

Flying, haste
Whenever Pyrus, the Undying Flame attacks, add {R}{R}{R}{R}. You don't lose this mana as steps, phases, and turns end.
{1}{R}: Pyrus gets +1/+0 until end of turn.

Trample
Whenever Quakestep Behemoth or another creature you control enters, put X +1/+1 counters on each creature you control, where X is the entering creature's power.

When Quillback dies, you may shuffle him into his owner's library. If you do, return up to one target Shaman creature card and up to one target non-Shaman creature card from your graveyard to your hand.

Whenever another nontoken creature you control dies, you may return it to the battlefield tapped face down under its owner's control. It's a Forest land.
{4}{G}, Return a land you control to its owner's hand: Create a 3/3 green Wurm creature token. Activate only as a sorcery.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast a noncreature spell, draw a card.
At the beginning of your end step, if you have four or more cards in hand, transform Rahstahde.

Whenever an Aura you control becomes attached to a creature, choose one —
• Raiding Gnoll-Band deals 3 damage to that creature.
• That creature gets +3/+0 until end of turn.

Flying, haste
{2}{R}{R}, Exile a multicolored card from your graveyard: Return Rainbow Phoenix from your graveyard to the battlefield tapped. If it's your declare attackers step, it enters attacking.

Flying
{B}: Target attacking creature gets +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.)

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.)

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.)

When Ravenous Abomination enters, choose one —
• Create two Treasure tokens.
• Put a +1/+1 counter on Ravenous Abomination.

Ravenous Grue enters with a menace counter on it.
{5}{B}{B}, Remove a menace counter from Ravenous Grue: Destroy target creature.

Creature tokens you control get +1/+1 and can block an additional creature each combat.

Flying

Reach
Whenever you cast a spell with mana value 5 or greater, Reaper Squad deals 3 damage to target player or planeswalker.

{2}{B}: Reclaimed Kalak gains indestructible until end of turn.
Revive {3}{W} ({3}{W}, 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.)

Flash
{U}, Return another creature you control to its owner's hand: Reclusive Archmage can't be blocked this turn and gains hexproof until end of turn. Activate only once each turn.

Trample, haste
When Red Pelt Hart deals combat damage to a player, return it to its owner's hand.
At the beginning of your end step, sacrifice Red Pelt Hart.

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

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.)

If one or more -1/-1 counters would be put on a creature an opponent controls, put twice that many -1/-1 counters on it instead.