msem-instigator

Put a +1/+1 counter on each of up to X target creatures.
Augmented — If you've spent {W}{U}{B}{R}{G} to cast spells this turn, instead put three +1/+1 counters on each of those creatures. They gain trample until end of turn.

When Biohazard enters the battlefield, destroy all other nonland permanents with mana value X or less.
At the beginning of each end step, each opponent loses life equal to the number of cards they've drawn this turn plus the number of spells they've cast this turn.

Flying
Whenever Blade of Reckoning deals combat damage to a player, that player sacrifices an untapped permanent.

Advance {1}{R}{W}{B} (Cast this for {1}{R}{W}{B} to advance it as it enters. {1}{R}{W}{B}: Advance this as a sorcery.)
Whenever Blastburn Angel advances, it gets +1/+1 and gains flying until end of turn. It deals 1 damage to each other creature.

({T}: Add {U}, {B}, or {R}.)
Bleak Dominion enters the battlefield tapped.

Gestalt (When this or another creature enters under your control, you may merge it with the one in play, keeping counters and attachments. They become the permanent on top plus all abilities from under it.)
This permanent gets +2/+2 for each card and token merged with it.

Whenever one or more creatures an opponent controls attack you or a planeswalker you control, that player gets a poison counter.

When Blessing of Roya enters the battlefield or whenever you cast a spell from a graveyard, you gain 5 life and you mill five cards. Then you may put a card from your graveyard on the bottom of your library.

Whenever you cast an instant or sorcery spell from exile, copy it. You may choose new targets for the copy.

Haste
Augmented — Whenever you cast a spell, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on Bolstered Guardian. It loses this ability and gains “Whenever this attacks, it deals 2 damage to each of up to two targets.”

Archive 5 (As this enters the battlefield, shuffle the top five cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Whenever a player discards a card, draw a card from the archived library.

[+2]: Discard a card at random. If you do, draw two cards.
[0]: Target creature's controller may pay X life. If they don't, you lose X life and gain control of it (Choose any number for X.)
[–3]: Flip a coin until you lose a flip or choose to stop flipping. For each flip you won, draw two cards and create a tapped Treasure token.

When Brand New Species enters the battlefield, create a tapped 3/2 green Horror creature token.
Augmented — At the beginning of each end step, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, put a +1/+1 counter on up to one target Horror you control.

Whenever you attack or cast a multicolored spell, put a +1/+1 counter on Brandy Axel.
If Brandy Axel would be destroyed, remove a +1/+1 counter from her. If you do, instead remove all damage from her and she deals 2 damage to each opponent.

Other creatures you control have haste.
Whenever Breach Titan enters the battlefield 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.

You may put a permanent card from your hand onto the battlefield. If it's a planeswalker, it enters the battlefield with five loyalty counters rather than any other amount, and you may activate its loyalty abilities this turn any time you could cast an instant.

If you would draw a card, you may instead choose creature or land and exile cards from the top of your library until you exile a card of the chosen type. Put that card into your hand and put all other cards exiled this way on the bottom of your library in a random order.

Shuffle your hand and graveyard into your library, then draw seven cards. You may have your life total become 10. You may cast a spell from your hand without paying its mana cost. Exile Bright Future.

Augmented — Whenever Bril, the Oltenen Emissary enters the battlefield or attacks, if you've spent {W}{U}{B}{R}{G} to cast spells this turn, destroy target permanent.

Defender
When Brine Duelist enters the battlefield, create a Treasure token. (It's an artifact with “{T}, Sacrifice this permanent: Add one mana of any color.”)
{W}{U}{B}{R}{G}: Put a +1/+1 counter on Brine Duelist. It loses defender.

Double strike
Whenever you cast a noncreature spell, you may choose one that hasn't been chosen —
• Tap or untap target permanent.
• Draw two cards, then discard a card.
• Creatures you control get +1/+1 until end of turn.

Flying
You may reveal the second card you draw each turn as you draw it. Whenever you reveal a nonland card this way, copy that card. You may cast the copy. If you don't, Brutal Director deals 2 damage to any target. (You still pay the spell's cost.)

Flying
Whenever a permanent you control becomes the target of a spell or ability you don't control, choose one —
• Create a 3/3 red Manticore creature token.
• Create two Treasure tokens.
• Draw a card.

Destroy all creatures. Each player shuffles their graveyard into their library.

Draw X cards, then abound. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)