msem-instigator

Flying, trample
Prismatic — Whenever you cast a multicolored spell, put a +1/+1 counter on Azure Caterwauler.

Whenever Babbling Experiment or another creature you control enters, target player mills two cards.

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.

First strike
Back-Alley Gnoll has lifelink as long as it's enchanted by a black Aura.
Back-Alley Gnoll gets +2/+0 as long as it's enchanted by a red Aura.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

When Backstage Broken enters, create a 1/1 colorless Construct Actor creature token.
Whenever a token you control leaves the battlefield, you gain 1 life.

Lifelink
At the beginning of your end step, if you gained life this turn, put a +1/+1 counter on Backstage Manager.

When Backstage Tinkers enters, you may return an artifact card from your graveyard to your hand.

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

Menace, haste

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.

This spell costs {U} less to cast if you dealt combat damage to a player this turn with a Rogue.
Flying
When Balloon Voyager enters, draw a card.

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
When Bane of Sanity enters, if it engorged a creature card, target player discards two cards.

When Baneblade Stalker enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

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

Lifelink
Forestcycling {1}, islandcycling {1} ({1}, Discard this card: Search your libary for a Forest or Island card, reveal it, put it into your hand, then shuffle.)

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.”

Vigilance
{1}{W}: Barbarian Axe Flinger gains double strike until end of turn.

When Barbarian Intimidator enters, target creature can't block this turn.
When Barbarian Intimidator enters, prevent all combat damage that would be dealt to target creature this turn.

Deathtouch
Whenever a creature dealt damage by Barbed Beast this turn dies, transform Barbed Beast.

Whenever Barker Duelist becomes blocked, defending player loses 1 life.
Unveil {3}{B}{R} ({3}{B}{R}: Transform this. Unveil only as a sorcery.)

When Barricade Patrol enters, create a 1/1 white Human Soldier creature token.
Whenever another creature you control dies, Barricade Patrol deals 1 damage to target player.

{1}{U}: Target creature you control can't be blocked this turn by creatures with less power.
{1}{U}: Target creature you control can't be blocked this turn by creatures with greater power.

When Basalt Ritualist enters, you may sacrifice a land or exile a land card from your graveyard. When you do, exile target creature, instant, or sorcery card from your graveyard. Until the end of your next turn, you may play that card. If that spell would be put into a graveyard, exile it instead.

Menace
Cat creatures you control have menace.
When Basat Priest enters, create a 2/2 white Cat creature token.