msem-instigator

Trample, prowess

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you casting a noncreature spell causes an ability of a creature you control to trigger, that creature gains your choice of first strike, haste, menace, or trample until end of turn.

Improve {1}{R} ({1}{R}: 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.)
When Siegebreaker Ogre enters, create two 1/1 red Goblin creature tokens with haste.

First strike

Menace
Whenever Skhorvall Warleader attacks, it gets +1/+0 until end of turn for each other attacking Warrior you control.

Haste, prowess
Wanderlust — When Spitfireling enters, if you control four or more differently named lands, create two 1/1 red Elemental creature tokens with prowess and haste.

If you would draw a card, you may skip that draw. If you do, create a tapped Treasure token and exile the top card of your library. You may play that card this turn.

When Sunset Cliffs Lawman enters, you may post a bounty on target creature. (Put a bounty counter on that creature. It has “When this creature dies, each opponent draws a card” as long as it has a bounty counter on it.)

Haste
Whenever The Marquess Devonport attacks, it deals 2 damage to you.
Attain {5}{R} ({5}{R}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Menace (This creature can't be blocked except by two or more creatures.)

Vanguard — Whenever a creature you control attacks alone, it gets +1/+1 and gains menace until end of turn.

When Timecrafter Lafterii enters, choose target permanent with one or more time counters on it, then put two time counters on it or remove two time counters from it.

Haste
When Treasure Haulers enters, you may salvage an artifact card. (Exile one from your graveyard until this creature leaves the battlefield. Whenever this creature deals combat damage to a player, put a card it salvaged into your hand.)

Undine Coven gets +1/+1 for each other Merfolk you control.
Whenever you cast a noncreature spell, Undine Coven deals 1 damage to target player or planeswalker.

When Viashino Glutton enters, you may have it consume. If you do, create two 1/1 red Goblin creature tokens. (To consume, sacrifice another creature or exile a creature card from your graveyard.)

Flying, haste
Whenever Vidal's Conjurant attacks, reveal the top six cards of your library. You may put an enchantment card with mana value 3 or less from among them onto the battlefield. If you do, sacrifice that enchantment at the beginning of the next end step. Put the rest on the bottom of your library in a random order.

At the beginning of your end step, create an X/X colorless Construct artifact creature token, where X is the number of artifacts that were put into your graveyard from the battlefield this turn.

Haste
When Volt Vermin enters, it deals damage to target player or planeswalker equal to the number of creatures with flash and/or haste you control.

Glorious end — When Warband Commander dies, if it was tapped, put a +1/+1 counter on each creature you control that attacked this turn.

Trample, haste
Defiance (Whenever this creature takes damage, if it survives and wasn't defiant, put a +1/+1 counter on it and it becomes defiant.)
Whenever Wastewolf attacks, it deals 1 damage to any other target.

Prowess
Whenever you cast a noncreature spell, target creature can't block this turn.

Survivors you control have double strike.

This spell costs {1} less to cast for each creature you control that attacked this turn.
First strike
Whenever Weavetide Militia and at least one other creature attack, creatures you control get +1/+0 until end of turn.

Whenever one or more creatures you control deal combat damage to a player or planeswalker, put a +1/+1 counter on target creature you control.

Improve {1} ({1}: 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.)
Once each turn, when one or more counters are put on a permanent you control, create a 1/1 colorless Human creature token.
Whenever you attack with three or more creatures, destroy up to one target artifact or enchantment.