msem-instigator

Whenever you cast a spell that's white, blue, black, or green, create a 1/1 white Soldier creature token.

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Maddened Elk attacks, it gets +1/+1 until end of turn for each other attacking creature you control.

Haste (This creature can attack and {T} as soon as it comes under your control.)
Double strike (This creature deals both first-strike and regular combat damage.)

Whenever an Actor you control becomes untapped, you may discard a card. If you do, draw a card.

Armed — Merciless Brute gets +2/+2 as long as it's equipped.

Haste
Whenever Mukal Charger attacks during your first combat phase each turn, untap all Constructs you control. After this phase, there's an additional main phase followed by an additional combat phase.
Respawn (When this creature dies, if it attacked this turn, return it to its owner's hand.)

Haste
Whenever Nadei deals combat damage to a player, that player sacrifices a land. You may put a land card from a graveyard onto the battlefield under your control.

First strike
Crew 1 (Tap any number of creatures you control with total power 1 or greater: This Vehicle becomes an artifact creature until end of turn.)

Survivors you control have haste.

Menace
When OM-6 Walker dies, OM-6 Walker deals damage to each player equal to twice the number of nonbasic lands that player controls.

Haste (This creature can attack and {T} as soon as it comes under your control.)
Olson's Sky Brigade has flying as long as you control another attacking Pirate.

Whenever Precursor Omniprocessor attacks, you may sacrifice an artifact or creature. If you do, put a +1/+1 counter on Precursor Omniprocessor and it gains menace until end of turn.
Crew 2 (Tap any number of creatures you control with total power 2 or greater: This Vehicle becomes an artifact creature until end of turn.)

Flying
When Pyre Apostle enters, discard your hand, then draw three cards.
Madness {3}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Haste
When Qilan Stormers enters, it gets +X/+0 until end of turn, where X is the number of creatures you control.

Trample

Whenever you cast a noncreature spell, Rageborn Pyromancer gets +1/+1 until end of turn.
{1}{R}: Rageborn Pyromancer gets +1/+0 and gains flying until end of turn.

Flying
When Rahstahde Persecutor enters, you may pay {2}{R}. When you do, it deals 4 damage to target creature.

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.

At the beginning of combat on each of your turns, you may sacrifice a land or exile a land card from your graveyard. If you do, create two 1/1 red Goblin creature tokens with haste. Exile those tokens at the beginning of the next end step.

If a player taps a nonbasic land for mana, that land produces {C} instead of any other type.
Whenever Rylei Wakebreaker attacks, it and another target creature you control each get +1/+0 until end of turn for each attacking creature you control.

When Sandmouth Dragon enters, another target creature you control gets +3/+0 until end of turn.
Mirage {2}{R} (You may cast this spell as though it had flash for its mirage cost. If you do, sacrifice it at the beginning of the next cleanup step.)

Flying
Tap five untapped Satrapies you control: Untap all creatures you control. After this main phase, there is an additional combat phase followed by an additional main phase. Activate only as a sorcery.

Whenever you cast a spell, if mana from an artifact was spent to cast it, exile the top card of your library. You may play that card until you exile another card with Savant of Cables.

First strike
Disgraced 1 (This enters with a -1/-1 counter. Whenever it deals combat damage to a player, remove all -1/-1 counters from it.)