msem-instigator

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.”

Look at the top ten cards of your library. Put any number of legendary permanents with total mana value 6 or less from among them onto the battlefield. Put the rest on the bottom of your library in a random order.
For each planeswalker you control, you may activate one of their loyalty abilities. (You still pay its costs.)

Flying
When Blackblood Feaster enters, you may have each player sacrifice a creature.
Pay 2 life: Blackblood Feaster gets +2/+2 until end of turn. Activate only once each turn.

Flying, lifelink
Whenever Blackhearted Sphinx attacks, you may pay 3 life. If you do, draw a card.

When Blackwall Ramparts enters, exile up to two target nonland permanents you don't control with total mana value 8 or less until Blackwall Ramparts leaves the battlefield.
Whenever you draw a card, you gain 1 life.

At the beginning of your upkeep, create two 1/1 colorless Construct artifact creature tokens, then you gain life equal to the number of artifacts and enchantments you control.

Lionize {2}{R} ({2}{R}, Exile this card from your hand: Put a +1/+1 counter on target creature and it gains the following abilities until end of turn. You may cast this card on a later turn from exile.)
Trample
This creature gets +3/+0 as long as it's attacking.

Flying
{1}, Sacrifice another creature: Regenerate target Vampire.

Trample
Bloodthirsty Berserkers can't be blocked by more than one creature.

Menace (This creature can't be blocked except by two or more creatures.)
Cycling {R} ({R}, Discard this card: Draw a card.)

Whenever a creature dies, put a +1/+1 counter on Bog Apex.

Your life total becomes 20.
Coalesce {8}{W}{W}{W}{W} (You may cast this from your graveyard for {8}{W}{W}{W}{W}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)
Born Anew's power and toughness are each equal to your life total.

Braineater Abominus can't be blocked by creatures with power 4 or greater.
Whenever a creature you control deals combat damage to a player, exile the top card of that player's library. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any type to cast it.

Double strike
{1}{R}{W}: Target creature gains double strike until end of turn. Activate only if Bravery is in your graveyard.

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.

When Bridled Narwhal enters, you gain 5 life.

Flying
When Brilliant Griffin enters, target creature gets +2/+2 until end of turn.

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

{6}{U}: Brume Trench-Thrasher can't be blocked this turn. This ability costs {1} less to activate for each instant and sorcery card you own in exile and in your graveyard.