msem-instigator

(Add a quest counter as this enters. Sacrifice after 3.)
Whenever another artifact or enchantment you control enters, add a quest counter.
1, 2 — You gain 3 life.
3 — Mill three cards, then return an artifact or enchantment card from your graveyard to the battlefield. Exile Seek the Maker's Egg.
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Whenever an Equipment you control enters, attach it to target creature you control.

Whenever you discard a card, exile that card from your graveyard.
{2}, {T}: Draw a card, then discard a card.
{4}, {T}, Sacrifice Bag of Holding: Return all cards exiled with Bag of Holding to their owner's hand.

Equipped creature gets +2/+2.
Whenever equipped creature attacks, each opponent who controls more artifacts than you sacrifices an artifact. Opponents sacrifice creatures, enchantments, lands, and planeswalkers the same way.
Equip {1}{W}

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.

First strike
When Enlistment Officer enters, reveal the top four cards of your library. Put all Soldier cards revealed this way into your hand and the rest on the bottom of your library in any order.

Target player discards a card.
Amass Soldiers 1. (Put a +1/+1 counter on an Army you control. It's also a Soldier. If you don't control one, create an 0/0 black Soldier Army creature token first.)

When Pelt's Refuge enters, if {G} was spent to cast it, distribute two +1/+1 counters among creatures you control.
Whenever a creature you control dies, draw a card.

Target creature you control gets +3/+3 until end of turn. Then if that creature has power 10 or greater, each other creature you control gets +3/+3 until end of turn.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{3}{B}{B}: Choose any number of other nontoken creatures you control. Whenever one of those creatures dies this turn, create a token that's a copy of that creature, except it has no mana cost.

Whenever one or more creatures you control with counters on them attack, draw a card.

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

Deathtouch
When this creature enters, if you cast it, target creature card in your graveyard gains arise until end of turn. Its arise cost is equal to its mana cost. (Exile that card from your graveyard and pay its arise cost as a sorcery: Create a black token copy of it that's also a Zombie and can't block.)

{1}{W}: Untap Steadfast Infantry.

When Monastery Scribe enters, return target instant or sorcery card from your graveyard to your hand.

Flying, first strike, lifelink

Skavi Behemoth can't be the target of nongreen spells or abilities from nongreen sources.

Flash
When Notorious Smuggler enters, target opponent reveals their hand. Choose a nonland card revealed this way. Copy it. You may cast the copy this turn. (You still pay its costs, including color. Copies of permanents enter as tokens.)

Sunwing has flying as long as it's your turn.

Haste
Motley — At the beginning of your upkeep, if there are five or more names among nonland permanents you control, Scarletblood Hound deals 3 damage to each opponent.

Menace
When Kai'Zhou enters, you may have all legendary nonland permanents phase out until your next turn.
Whenever Kai'Zhou deals combat damage to a player, they sacrifice a legendary permanent.

Whenever Caldera Crawlers attacks, you may sacrifice a land or exile a land card from your graveyard. If you do, target creature gets +1/+1 and gains menace until end of turn.

Reverberate {3}{U} (When you cast this spell, copy it if you paid its reverberate cost. You may choose new targets for the copy.)
Create a token that's a copy of target creature you control.

At the beginning of combat on your turn, target creature you control gains vigilance until end of turn. That creature can't be blocked this turn.

Menace
When Rattled Bones dies, forebode. (Create a tapped colorless Omen artifact token with “{T}, Discard a card, Sacrifice this artifact: Draw a card.”)