msem-instigator

Whenever Drownyard Colossus or another creature you control enters, any number of target players each mill cards equal to that creature's toughness.
{2}{U}{B}, {T}: Draw a card, then create a 0/3 blue Crab creature token with “{T}: Target player mills a card.”

Flying, haste
Whenever Eavesknocker attacks, another target attacking creature gets +1/+1 until end of turn.

First strike
Whenever Edgar Markov, Bloodsire attacks, exile the top three cards of your library. You may play those cards until end of turn.
Whenever another Vampire you control enters, it deals damage equal to its power to any target.

{T}: Add one mana of any color.
Whenever you cast a foreshadowed spell, create a 2/2 black Zombie creature token.

Indestructible
Ghrin-Danu, the Dawnhart can't attack or block unless you control three other creatures with different powers.
Whenever you attack, put a +1/+1 counter on up to one other target creature you control.

When Gift of the Seraph enters, exile target nonland permanent an opponent controls until Gift of the Seraph leaves the battlefield. When you do, create a Weapon token and attach it to up to one target creature you control. (A Weapon token is an Equipment artifact with “Equipped creature gets +1/+1” and equip {2}.)

Flying, first strike, haste
Whenever you gain life, you may have Gisela, Blade of Morning deal that much damage to any target. Do this only once each turn.

Flying
When Goldnight Seraph enters, it deals X damage to up to one target creature or planeswalker and you gain X life, where X is the number of artifacts you control.

Greater Sangromancy deals 4 damage to any target. If a permanent dealt damage this way would die this turn, exile it instead. Create a 1/1 black and red Vampire creature token with menace.

When Hamlet Swordmaster enters, create a Weapon token. (It's an Equipment artifact with “Equipped creature gets +1/+1” and equip {2}.)
Whenever Hamlet Swordmaster attacks while you control three or more artifacts, exile the top card of your library. You may play it this turn.
Artifact spells you cast cost {1} less to cast.

Reach
As long as you control an artifact or an enchantment, Heron's Grace Patrol gets +1/+1 and has vigilance.
{2}{G}{W}, {T}: Mill three cards. You may return a permanent card milled this way to your hand.

When Kessig Wolftamer enters, create a 2/2 green Wolf creature token.
{4}{R}{G}: Transform Kessig Wolftamer. Activate only if it's attacking.

Whenever Krallenhorde Instigator deals combat damage to a player, create a 2/2 green Wolf creature token.
At the beginning of your end step, if Krallenhorde Instigator didn't attack this turn, transform it.

Menace
You may spend mana as though it were mana of any color to cast double-faced spells or activate abilities of double-faced sources.
Once during each of your turns, you may cast a double-faced spell you own from outside the game.

Other Wolves and Werewolves you control have haste.
Leyran Hunting Pack gets +1/+1 for each non-Human Werewolf you control.

Flying, lifelink
Liesa has haste as long as it was foreshadowed.
When Liesa dies, each opponent sacrifices a creature and loses 2 life.
Foreshadow {4}{W}{B} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

When Liturgy of Brine enters, draw a card, then you may put a land card from your hand onto the battlefield tapped.
Invocation — Whenever you spend four or more mana to cast a spell or activate an ability during your turn, Liturgy of Brine becomes a 5/5 Kraken Horror creature in addition to its other types until end of turn.

If a creature entering causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.
[+1]: Target player draws two cards, then discards a card. Put a +1/+1 counter on up to one target creature you control.
[–3]: Create a token that's a copy of target creature you control.
[–8]: Return any number of target nonland permanents to their owner's hand.

You have no maximum hand size.
Whenever Makodonis's Wolfbro attacks, if its power is greater than its base power, draw cards equal to the difference.

This spell costs {2} less to cast for each Curse you control.
Flying, vigilance, haste

When March of the Unhallowed enters, mill three cards, then return a creature card with mana value 3 or less from your graveyard to the battlefield.
Whenever you attack with three or more creatures, each opponent loses 1 and you gain 1 life.

Mortalcoil Hydra enters with a number of +1/+1 counters on it equal to the amount of mana spent to cast it.
When Mortalcoil Hydra dies, each opponent loses 3 life and you gain 3 life.
Foreshadow {4}{B}{G} (You may cast this spell for its foreshadow cost. If you do, also trigger its “dies” abilities when it enters.)

Flying
Whenever Olivia Voldaren, Progenitrix attacks, you may discard a card. If you do, draw a card.
Whenever you discard a creature card, put a +1/+1 counter on Olivia Voldaren, Progenitrix and create a 1/1 black and red Vampire creature token with menace.

Create three 1/1 white Spirit creature tokens with flying.

Menace
Whenever you cast a spell from your graveyard, The Selhoff Twins deals damage equal to that spell's mana value to any target. Then copy that spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)