msem-instigator

Flash
When Augmented Spawn enters, create a 1/1 blue Merfolk creature token for each Island you control.
{U}, Sacrifice a Merfolk: Augmented Spawn gains hexproof until end of turn.

Frenzy 2 (Whenever this creature attacks and isn't blocked, it gets +2/+0 until end of turn.)
Blocked creatures you control have first strike.

Each other colorless creature you control enters with an additional +1/+1 counter on it.

Vigilance
Avatar of Utsenchep can block any number of creatures.
All creatures able to block Avatar of Utsenchep do so.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever a nontoken creature you control enters, you may pay {1}{W}. If you do, create a 1/1 white Bird creature token with flying.

This spell costs {2} less to cast if a creature died under your control this turn.
Flying

Create a 5/3 black Horror creature token.
Flashback {1}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Draw X cards, where X is the number of differently named lands you control.

Backstabbing Courtiers can't attack unless you foretold a card or cast a foretold spell this 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.)

Defender (This creature can't attack.)
Discard a card: Barge Engulfer can attack as though it didn't have defender until end of turn.

First strike (This creature deals combat damage before creatures without first strike.)
Other Soldier creatures you control get +1/+1 and have first strike.
{3}{W}: Create a 1/1 white Soldier creature token.

When Batrest's Forgemaster enters, you may search your library for an Equipment card, reveal it, put it into your hand, then shuffle.
Whenever Batrest's Forgemaster attacks, Equipment spells you cast this turn cost {2} less to cast.

Battalion — Whenever Battleborn Brute and at least two other creatures attack, Battleborn Brute gets +2/+2 until end of turn. Untap it.

Flying, lifelink

Inspired — Whenever Bearer of Vile Incense becomes untapped, create a 0/1 black Cultist creature token with “{1}{B}{B}, Sacrifice three Cultists: Create a 5/5 black Demon creature token.”

Auras and Equipment you control have indestructible.
Whenever Bearidge Marshall attacks, you may create a white Aura enchantment token named Arrest attached to target creature. It has enchant creature and “Enchanted creature can't attack or block, and its activated abilities can't be activated.”

If you control ten or more nonland permanents, you get an emblem with “At the beginning of your end step, return target permanent card from your graveyard to the battlefield.”
Destroy all nonland permanents.

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)

Aetherize each permanent you control. Exile Beneath the Horizon. (To aetherize a permanent, create a token that's a copy of it, then exile that token.)

When Benthic Shipcrasher enters, scry 3.

Armed — Whenever Beragnian Intimidator attacks, if it's equipped, target creature can't block this turn.

Flying
Sacrifice six Swamps: Return Berbarus Unsealed from your graveyard to the battlefield with an indestructible counter on it. You draw six cards and you lose 6 life.

Trample
Bessie's Crusher has haste as long as you control another Wurm.

[+2]: Create a 3/3 red Wurm creature token.
[–2]: Up to three target creatures each get +2/+2 until end of turn. Bessie deals 2 damage to each of up to three target creatures.
[–9]: You get an emblem with “Creatures you control have base power and toughness 7/7 and have indestructible.”