msem-instigator

Barren Boneyard enters tapped.
{T}: Add {B}.
{2/B}{2/B}: Barren Boneyard becomes a 2/3 black Elemental creature with deathtouch until end of turn. It's still a land.

As Barren Desolation enters, you may pay 2 life. If you don't, Barren Desolation enters tapped.
{T}, Sacrifice Barren Desolation: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever Barrow Banshee deals combat damage to an opponent, that player discards a card at random.

Each planeswalker you control enters with an additional loyalty counter on it.
{T}: Add {C}.

Whenever you untap a nonland permanent, put a winding counter on Barton's Pocketwatch.
{T}: Look at the top card of your library. You may put it into your graveyard. Then if Barton's Pocketwatch has twelve or more winding counters on it, exile it and take an extra turn after this one.

Flash
Once each turn, you may cast a spell without paying its mana cost. If you do, at the beginning of your next upkeep, you lose the game unless you pay that spell's mana cost.

Basin Fortress enters tapped unless you control a basic land.
{T}: Add {B} or {G}.

Flying, first strike, vigilance, lifelink
When Bastion Valkyrie dies, create three Function tokens with “Choose a creature targeted by this spell. It gains flying, first strike, vigilance, and lifelink until end of turn.” (They're enchantments. As you cast an instant or sorcery spell, sacrifice any number of Functions to add their effects to that spell.)

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.

Renown 2 (When this creature deals combat damage to a player, if it isn't renowned, put two +1/+1 counters on it and it becomes renowned.)
Whenever a creature you control becomes renowned, draw a card.

Return any number of target creature cards with total mana value X or less from your graveyard to the battlefield, where X is the number of cards in your graveyard. Exile Battle at the Boneyard.

As Battle for the Shield enters, choose Danuri or Fellor.
• Danuri — Soldiers you control get +0/+1 and have vigilance.
• Fellor — Warriors you control get +1/+0 and have first strike.

As Battle the Evil One enters, choose Evil One or Rehison.
• Evil One — Zombie creature cards in your graveyard have unearth {3}{B}. ({3}{B}: Return this card from your graveyard to the battlefield. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)
• Rehison — Whenever an Elf you control enters, you may put a -1/-1 counter on target creature.

Whenever one or more creatures you control attack, you may put a progress counter on Battlesuit Prototyping.
[progress 2-6] Creatures you control get +1/+1.
[progress 7+] Creatures you control get +2/+2 and have indestructible.
Creatures you control get +2/+2 and have indestructible.

Deathtouch, lifelink
Whenever Batwing Initiate deals combat damage to a player, put a +1/+1 counter on it.
Pay 4 life: Batwing Initiate gains flying until end of turn.

At the beginning of your upkeep, Bauble of Infinites deals 2 damage to each opponent and you gain 2 life.

(Transform this if it's not attached to a creature. Pay {1}{U} as a sorcery to unattach it.)
Enchant creature you control
Bay-Bandit's Snapper's rider gets +1/+2.
Whenever Bay-Bandit's Snapper's rider deals combat damage to a player, you draw two cards.

Flash
Haste
{3}, {T}: Exchange control of two target noncreature spells. Their controllers may choose new targets for the spells.

If you would catalyze, catalyze twice instead. (The next spell you cast this turn costs {1} less to cast.)
You may pay an additional {2} as you cast a spell. If you do, reveal the bottom card of your library. You may put it into your graveyard or on top of your library.

When Bearer of Silk Chains enters, gain control of target nonland permanent until Bearer of Silk Chains leaves the battlefield. If that permanent is a Horror, gain control of it instead.

When Bearer of Tormented Truths enters, look at target player's hand. You may exile a nonland card from among them. If you do, that player draws a card.
You may play cards exiled with Bearer of Tormented Truths, and you may spend mana as though it was mana of any color to cast them.

When Bearer of the Lantern enters, you gain 3 life.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Whenever an artifact or enchantment you control enters, you may detain target nonland permanent. (Until your next turn, that permanent can't attack or block and its activated abilities can't be activated.)

Whenever you detain a permanent, you gain life equal to that permanent's mana value.

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.”