msem-instigator

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Beastback Raider desecrates a permanent, discard your hand, then draw three cards.

{2}{G}: Target face-down creature you control becomes a Beast with base power and toughness 5/5 until end of turn.

Damage can't be prevented this turn. Beat & Batter deals 2 damage to target player, then 2 damage to each player that's gained life this turn.

Menace
When Beatrice enters, target opponent reveals their hand. Exile a nonland card from it. During any turn that player lost life, you may cast that card and mana of any type can be spent to cast that spell.

Whenever Beatrice's Dodger attacks, create a 1/1 black and red Human Rogue creature token that's tapped and attacking.
{3}{B}{R}: Return Beatrice's Dodger from your graveyard to the battlefield
tapped and transformed.

Sabotage — Whenever an opponent or permanent an opponent controls becomes the target of a spell you control, put a quest counter on Beckon Darkness.
At the beginning of your upkeep, if Beckon Darkness has four or more quest counters on it, return target creature card from your graveyard to the battlefield.

As an additional cost to cast this spell, sacrifice a creature.
Search your library for a creature card with mana value equal to the sacrificed creature's mana value minus 1, put it onto the battlefield, then create a token that's a copy of that creature. Then shuffle.

Whenever you cast an enchantment spell, you draw a card and you lose 1 life.
Whenever one or more counters are put on an enchantment you control, you gain 1 life and each opponent loses 1 life.

Draw a card, then reveal any number of creature or land cards from your hand. You gain that much life.

Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Bedfellow can't block or be blocked.
Exile two cards from your graveyard: Bedfellow gets +1/+1 until end of turn.

Insects you control have hexproof.
At the beginning of your end step, if you control a nontoken Insect, create a 1/1 green Insect creature token.

X target creatures can't block this turn.
Fuse (You may cast one or both halves of this card from your hand.)

When Belief in the World enters, you may tap two untapped creatures you control. If you do or you control two or more Spirits, search your library for a Spirit card, reveal it, put it into your hand, then shuffle.
Creatures you control get +1/+1.

Enchant creature you control
Enchanted creature gets +3/+3.
When Belligerence enters, enchanted creature fights target creature an opponent controls.
When enchanted creature dies, if it's a Warrior, return Belligerence to its owner's hand.

Whenever a creature you control dies, you may search your library for a creature card with lesser mana value, put it onto the battlefield tapped, then shuffle. Do this only once during each of your turns.

(Transform this if it's not attached to a creature. Pay {2}{B}{B} as a sorcery to unattach it.)
Enchant creature you control
Belmord Blood-Coach's rider gets +3/+3 and has deathtouch.
Whenever Belmord Blood-Coach's rider attacks, you may return target creature card with mana value less than its rider's power from your graveyard to the battlefield tapped.

Other Knights and Soldiers you control get +1/+0.
Cowards can't block Knights and Soldiers you control.
When Belmord Bloodcurdler enters, target creature an opponent controls becomes a Coward in addition to its other types. (This effect last indefinitely.)

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.

Flying
When Benevolent Malach enters, create a 1/1 colorless Construct artifact creature token.
Sacrifice Benevolent Malach: Artifacts you control gain indestructible until end of turn.

[+1]: Creatures you control get +1/+0 and gain haste until end of turn.
[0]: Bennett Brooks deals 2 damage to each opponent. If you have an insight counter, create two Treasure tokens.
[0]: You get an insight counter.
[–2]: Sacrifice an artifact. If you do, return target artifact card from your graveyard to the battlefield.

When Benthic Tidebreaker enters, reveal the top card of each player's library and exile one of those cards. You may play that card for as long as it remains exiled, and you may spend blue mana as though it were mana of any color to cast it.
Evoke {1}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

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.

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.