msem-instigator

Assault {B} (Whenever this attacks, if it has no +1/+1 counters on it, you may pay its assault cost to put a +1/+1 counter on it.)
When Hilaback Outriders assaults, it gains menace until end of turn.

Submerge all creature cards in graveyards. (To submerge a card, exile it, then put it on the battlefield face down under its owner's control as a 2/2 creature.)

Distorted (This creature can be blocked by tapped creatures but not untapped creatures.)
Other creatures you control with distorted get +2/+2.

When El, Humble Apprentice enters, search your library for a basic land card, reveal it, put it into your hand, then shuffle.
Chosen one ({W}{U}{B}{R}{G}: Transform this permanent.)

Whenever a player looks at one or more cards in your library or searches your library, Lavamind Elemental deals 2 damage to that player. (This includes you.)
At the beginning of your end step, look at the bottom card of your library. You may put it on top of your library.

Target creature gets -1/-1 until end of turn.
Flashback {1}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Lightwalker has flying as long as it has a +1/+1 counter on it.

Flash
Enchant creature
When Arcane Anesthesia enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

First strike
When Mutilated Warrior enters, you may have it deal damage to each player equal to the number of Warriors you control.

Whenever Herald of Purity is dealt damage, it deals that much damage to any target.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Choose target creature you control and target creature you don't control. Flip a coin. If the coin comes up heads, put one of those creatures on top of its owner's library. Otherwise, put both of them on top of their owners' libraries.

Search your library for a card, put it into your hand, shuffle, then add three mana in any combination of colors.
{1}, Discard Tahli's Council: Add one mana of any color. Scry 1.

Whenever another nontoken creature you control enters, if it doesn't share a name with another creature you control or a creature card in your graveyard, put a +1/+1 counter on Guardian of the Divergent.

Gain control of target creature until end of turn. Untap that creature. Until end of turn, it gets +1/+0 and gains haste.

Choose five. You may choose the same mode more than once.
• Each opponent sacrifices a creature or planeswalker.
• You draw a card and you lose 1 life.
• Each opponent loses 2 life.
• Each opponent discards a card.

Create three 1/1 red Goblin creature tokens.

[+1]: Return a land you control to its owner's hand. Create a tapped colorless land token named Far-Off Lands with “{T}: Add one mana of any color.”
[–1]: Discard a card. Return to your hand a card from your graveyard that shares a color with that card or a color of mana it could produce.
[–3]: For each color pair, you may pay that mana. Create X X/X green and blue Elemental creature tokens, where X is the number of times you do.

Hexproof
When Wary Watchkeeper enters, target player mills three cards.

Whenever you make first contact, create a Treasure token. (You make first contact the first time each turn you cast a spell with a name not in your graveyard or control already.)
{T}, Return an artifact with mana value X you control to its owner's hand: You may cast a spell with mana value X plus 1 or less and with a different name from your hand without paying its mana cost.

When Campaign Recruiter enters, you may search your library for a creature card with first strike, double strike, flying, improve, lifelink, melee, or vigilance, reveal it, put it into your hand, then shuffle.

Love Letters enters with X stamp counters on it.
Whenever one or more creatures you control deal combat damage to a player, you may remove a stamp counter from Love Letters. If you do, draw a card.

Whenever you cast a spell from anywhere other than your hand, you may sacrifice a creature. If you do, copy that spell. You may choose new targets for the copy.

When Esiara, Skycaster's Infiltrator enters, exile target spell with mana value 4 or less.
{1}{U}{U}, Discard two cards: Exile Esiara, then return it to the battlefield under your control.
{2}{U}{U}, {T}, Exile Esiara: Until end of turn, you may play cards you don't own from exile.

When Skittering Atrocity enters, up to one target creature gets -X/-X until end of turn, where X is the number of Horrors you control.

Attacking creatures have winnow. (Damage dealt to a creature with winnow also causes its controller to lose that much life.)