msem-instigator

At the beginning of combat on your turn, target creature you control has base power and toughness 5/5 until end of turn.

Whenever you cast a noncreature spell, Pirates and Rogues you control get +1/+0 and gain trample until end of turn.
Whenever this creature deals combat damage to a player, you may sacrifice it. If you do, return target instant or sorcery card from your graveyard to your hand.

Creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, Bellowing Thoctar gets +2/+2 until end of turn.

Flash
Lifelink
When this creature enters, counter target spell unless its controller pays {1} or 3 life.

Choose target creature with the greatest power or tied for the greatest power, then destroy all other creatures.

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 Alchemist enters, draw a card, then discard a card, then mill a card.
Whenever you cast an instant or sorcery spell, create a 1/1 colorless Elemental creature token. It gains haste until end of turn.

Whenever Beragnian Brawlmaster or another Warrior you control enters, that Warrior fights target creature an opponent controls.
{R}{W}: Target Warrior creature gets +1/+1 until end of turn.

Prevent all combat damage that would be dealt to and dealt by Bereaved Aristocrat.
Unveil {2}{W}{U} ({2}{W}{U}: Transform this. Unveil only as a sorcery.)

At the beginning of your upkeep, mill a card.
Whenever a creature card is put into your graveyard from anywhere, if that card has flying, you may put a flying counter on Berylscale Alaj. Repeat this process for first strike, double strike, deathtouch, hexproof, lifelink, menace, reach, trample, and vigilance.

[+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.”

Bestial Mob's power and toughness are each equal to the number of creatures you control.
Whenever Bestial Mob deals combat damage to a player, destroy target creature with toughness less than Bestial Mob's power.

You may have Better Half enter as a copy of any creature on the battlefield, except it's a Reflection in addition to its other creature types and it has distorted. (It can be blocked by tapped creatures but not untapped creatures.)

Trample, haste, indestructible
Whenever a permanent an opponent controls is put into a graveyard from the battlefield, put a +1/+1 counter on target Ooze.

When Bind the Mind enters, each poisoned opponent reveals their hand. Then choose a nonland card name.
Spells with the chosen name can't be cast.

When Biohazard enters, 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.

Create a 1/1 blue Bird creature token with flying. (Cast a copy of this spell once while this creature is on the battlefield.)

Legacy (You may play this side of this card only from your graveyard. Exile it if it would leave the battlefield or not resolve.)
Permanents you control have lifelink and “{T}: Add one mana of any color.”

You may reveal a Knight or Soldier card from your hand as you cast this spell. If you do or you control one as you cast it, you may cast it as though it had flash and it can't be countered.
Exile target nonland permanent with mana value 3 or less.

At the beginning of your end step, mill two cards. Then if ten or more cards are in your graveyard, transform Bitter Duckling.

When Bitter Pact enters, destroy target nonbasic permanent.
All permanents and players lose hexproof, indestructible, and protection and can't have or gain hexproof, indestructible, or protection.

Return to your hand all permanent cards in your graveyard that were put there from the battlefield this turn.

When Bjarndyr Mender enters, other creatures you control get +1/+1 and gain indestructible until end of turn.

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