msem-instigator

Equipped creature can't be blocked except by enchantment creatures.
Whenever equipped creature deals combat damage to a player, you may search your library for a card, exile it, then shuffle. If you don't search your library this way, you may play a card exiled with Runner's Harness.
Equip {1}

[+1]: Exile the top card of your library. When a source you control deals damage to an opponent this turn, put the exiled card into your hand.
[–2]: Exile target nonland permanent. Its controller reveals the top card of their library, then puts it onto the battlefield if it's a permanent card.
[–6]: Exile your library. You may play cards exiled this way for the rest of the game.

Flash
{1}{W}: Exile target creature that dealt damage to you this turn until The Shield leaves the battlefield.

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When Nizev Brawler enters, target creature can't block this turn.

When Burglar Cat enters, exile the top card of target opponent's library. You may play that card during any turn you attacked with a Rogue, and you may spend mana as though it were mana of any color to cast it.

{T}: Add {G} or {U}. You lose 1 life unless you have less life than an opponent.

Flying
Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever a marked creature dies, you gain 2 life.

When Marauder's Broadsword enters, you may pay {1}. If you do, create a 1/1 white Soldier creature token and attach Marauder's Broadsword to it.
Equipped creature gets +2/+0.
Equip {2}

When Dunesea Merchant enters, tap up to X target creatures, where X is the number of Satrapies you control.
Satrapycycling {2} ({2}, Discard this card: Search your library for a Satrapy card, reveal it, put it into your hand, then shuffle.)

Whenever Duskwatcher attacks, create a Function token with “Tap target creature.” (It's an enchantment. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

Equipped creature has all activated abilities of all creature cards in your graveyard.
Equip {3}

Menace (This creature can't be blocked except by two or more creatures.)
Whenever a creature you control deals combat damage to a player, you may have Aspect of Rage deal 1 damage to any target.

Mill four cards, then return a creature or enchantment card from your graveyard to you hand. You gain 3 life.

Put target creature on top of its owner's library. You create a token that's a copy of that creature.

Civilized — Hard-Working Oxen gets +3/+0 as long as you control an artifact, a creature, and an enchantment.

Converge — Each creature gets -X/-X until end of turn, where X is the number of colors of mana spent to cast Enjoy the Silence.

Other creatures you control have haste.
Whenever Breach Titan enters or attacks, abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)
At the beginning of your end step, return another target creature you control to its owner's hand.

Exile any number of nonland permanents you control. Return them to the battlefield at the beginning of the next end step.
Reconstruct {7}{U} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

If Professor Haldean would leave the battlefield, exile him instead.
Whenever you cast a spell, you may untap Professor Haldean and another target permanent.
{T}: Professor Haldean deals 1 damage to each opponent.

When Paralysis Specialist enters, up to two target creatures don't untap during their controller's next untap step.

First strike
Whenever Guardian of the Eclipse attacks, you may exile another target attacking creature you control, then return it to the battlefield under your control tapped and attacking.

You may exert Awoken Elemental as it attacks. When you do, Awoken Elemental fights another target creature. (An exerted creature won't untap during your next untap step.)

Equipped creature gets +3/+0.
Whenever a creature you control attacks and isn't blocked, you may pay {4}. If you do, attach Feral Cleaver to that creature.
Equip {3}

Until end of turn, creatures you control get +1/+1 and gain trample and poisonous 1. (Whenever one of those creatures deals combat damage to a player, that player gets a poison counter.)

Bronze Giant has trample as long as you control a token creature.