msem-instigator

Lifelink
When Black Curtain Enforcer enters the battlefield, you may return target creature card with mana value 3 or less from your graveyard to your hand.

Flying
When Blackblood Feaster enters the battlefield, 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.

When Blacksite Moderator enters the battlefield, you may pay 2 life or sacrifice a permanent. If you do, draw a card.

When Blackwall Ramparts enters the battlefield, 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.

When Blackwall's Edge enters the battlefield, if you control four or more lands, you may have each player conjure a card named Data-Point into their hand. (It's a sorcery that costs {2} with “Draw a card.”)
{T}: Add {C}.
When Blackwall's Edge is destroyed, return it to its owner's hand.

Flash
When Blade of Mautakesh enters the battlefield, creatures you control gain poisonous 1 until end of turn. (Whenever those creatures deal combat damage to a player, that player gets a poison counter. Multiple instances of poisonous trigger separately.)

When Blazeblade Sergeant enters the battlefield, adjudicate. (Create a white Aura enchantment token with enchant creature and “Sacrifice this token: Untap enchanted creature” attached to target creature.)
Whenever an Aura enters the battlefield under your control, target creature you control gains first strike until end of turn.

Trample, haste
When Blazing Fox enters the battlefield, you may tap an untapped creature you control. If you do, Blazing Fox gets +X/+0 until end of turn, where X is that creature's power.

Flying
When Bleak Condor enters the battlefield, mill four cards.

When Bleak Gorge Convoy enters the battlefield, you may search your library for a Desert card, put it onto the battlefield tapped, then shuffle.

Flying
Menagerie — When Bleakrealm Mini-Menace enters the battlefield, if there are five or more creature types among creatures you control, it deals 2 damage to target opponent and 2 damage to up to one target creature or planeswalker that player controls.

When Blessing of Roya enters the battlefield or whenever you cast a spell from a graveyard, you gain 5 life and you mill five cards. Then you may put a card from your graveyard on the bottom of your library.

When Blightbringer enters the battlefield, creatures your opponents control get -1/-1 until end of turn.
Unearth {3}{B} ({3}{B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the end step or if it would leave the battlefield. Unearth only as a sorcery.)

When Blighting Ooze enters the battlefield, put a -1/-1 counter on each of up to X target creatures.
As long as Blighting Ooze is on the battlefield, it has all activated abilities of each creature with a -1/-1 counter on it.

Flash
Blind Blackguard can't block.
When Blind Blackguard enters the battlefield, target player draws a card, then reveals their hand. You choose a nonland card from that player's hand, then that player puts the chosen card on the bottom of their library.

When Blinding Fiddler enters the battlefield, until your next turn, creatures can't attack you or a planeswalker you control unless their controller pays {2} for each of those creatures.
Unveil {3}{W}{U} ({3}{W}{U}: Transform this. Unveil only as a sorcery.)

When Blood Jade Prophet enters the battlefield, reveal the top three cards of your library. For each card revealed this way, you may pay 3 life. If you do, put that card into your hand. Otherwise, put it into your graveyard.

Engorge (As this enters the battlefield, mill three cards, then exile a card from among the milled cards.)
When Blood Servant enters the battlefield, if it engorged a creature card, you draw a card and you lose 2 life.

Flying (This creature can't be blocked except by creatures with flying or reach.)
When Blood-Tithe Harpy enters the battlefield, target player loses 1 life and you gain 1 life.

Enchant creature
When Bloodbriar Blessing enters the battlefield, draw a card.
Enchanted creature gets +2/+2 and has menace.

Engorge (As this enters the battlefield, mill three cards, then exile a card from among the milled cards.)
When Bloodchill Risen enters the battlefield, if it engorged an instant card, return target creature to its owner's hand.

Bloodfell Caves enters the battlefield tapped.
When Bloodfell Caves enters the battlefield, you gain 1 life.
{T}: Add {B} or {R}.

Haste
When Bloodfury Warlord enters the battlefield or dies, it deals 2 damage to each player.

Flash (You may cast this spell any time you could cast an instant.)
When Bloodhunter Orca enters the battlefield, target opponent sacrifices a creature that was dealt damage this turn.

When Bloodpact Tormentor enters the battlefield, you may put a -1/-1 counter on target creature.
Bloodpact Tormentor can't be blocked by creatures with counters on them.