msem-instigator

When Babyscale Bruiser enters, you may reveal a creature card from your hand. If you do, Babyscale Bruiser deals damage to target creature an opponent controls equal to the revealed card's power. That creature deals damage equal to its power to Babyscale Bruiser.

Put two +1/+1 counters on target creature. Untap that creature.

You may cast target instant card from your graveyard this turn. If a card cast this way would be put into your graveyard, exile it instead.

Haste
When Backdrop Artisan dies, audition for red. (Create a 1/1 Construct Actor creature token, a Warrior Role giving 3/2 and trample, or a Wizard Role giving 2/2 and prowess. Roles replace older ones.)

Non-Actor creatures can't block this turn.

{T}, Pay 1 life: Add {R} or {W}.
{1}, {T}, Sacrifice Backstage Rooms: Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Whenever Backstreet Gutter-Runner attacks, if you control another Pirate or Rogue, it deals 2 damage to each opponent.

Basic Forests you control have “{G}, {T}: Untap target attacking creature and remove it from combat.”

When Backwoods Cultivator enters, put a +1/+1 counter on target creature you control.
When Backwoods Cultivator dies, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another kind of a counter already there.)

Menace, haste

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.

Deathtouch
Bahet's Emissary gets +1/+1 as long as you control a white or black permanent.

Double strike
Engage (This creature must be blocked each combat if able.)
{1}{R}: Balanced Blade gets +1/+0 until end of turn.

Prowess
Whenever Balefire Conjurer attacks, you may pay {1}{R}. If you do, exile the top card of your library. You may play that card until the end of your next turn.

Haste (This creature can attack and {T} as soon as it comes under your control.)
{1}{U}: Balloon Dragoon gains flying until end of turn.

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Lifecycle {3} ({3}, Discard this card: Create two tapped 1/1 colorless Elemental creature tokens.)

At the beginning of combat on your turn, if there are five or more creature types among creatures you control, creatures you control get +2/+0 and gain menace until end of turn.

Equipped creature gets +3/+0 and has vigilance.
Equip {3}

Reach
{4}{B}: Each opponent loses 2 life and you gain 2 life.

Haste
Whenever Banished Companion attacks, it deals 2 damage to you.

Gain control of target artifact or creature until end of turn. Untap it. If it's a creature, it gains haste until end of turn and up to one target creature can't block it this turn.

Trample
When Bank Skimmer enters, create a green Aura enchantment token named Turtle's Valor attached to target creature. The token has enchant creature and “Enchanted creature gets +X/+X, where X is its mana value.”

When Banner of Warfare enters, 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.)
{1}, {T}: Add one mana of any color.

Golden age (If you cast an instant or sorcery spell, activated a nonmana ability, and attacked this turn, enter a renaissance for this game.)
Baptism by Fire deals 3 damage to target creature or planeswalker. If you're in a renaissance, Baptism by Fire deals 6 damage to that permanent instead.

Trample
Whenever another Dwarf you control enters, create a colorless artifact token named Ale. It has “{T}, Sacrifice this artifact: Target creature gets +2/+0 until end of turn. Activate only as a sorcery.”