msem-instigator

This spell costs {1} less to cast for each creature with one or more counters on it.
Flying, vigilance

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

Sacrifice another creature: Put a +1/+1 counter on target creature you control. Activate only as a sorcery.

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

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.

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Bloodfall deals 8 damage divided as you choose among up to eight targets. If you spent exactly {R} for this spell's mana payment, it deals 8 damage to each of those targets instead.

Flying, menace, haste
When Bloodfiend Ravager enters, it deals 2 damage to any target. If a permanent dealt damage this way would die this turn, exile it instead.
Evoke {1}{R} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Flying, haste
{1}{R}{R}: Return Bloodfire Phoenix from your graveyard to the battlefield. Activate only if an opponent lost 3 or more life this turn.

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

Equipped creature gets +1/+1 and has lifelink.
Whenever equipped creature dies, if it wasn't a token, you may pay {3}. If you do, create a token that's a copy of that creature and attach Bloodguard's Hand to it.
Equip {3}

Whenever you discard a card or an artifact is put into your graveyard from the battlefield, put a +1/+1 counter on Bloodhollow Bruiser.
Cycling {2} ({2}, Discard this card: Draw a card.)

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

Sacrifice a creature: Put a +1/+1 counter on Bloodlash Caravan. Then if it's the only creature you control, it gains indestructible until end of turn.

Bloodline Zealot gets +2/+0 and has menace as long as you've sacrificed a permanent this turn.

Frenzy 1 (Whenever this creature attacks and isn't blocked, it gets +1/+0 until end of turn.)

When Bloodpact Collector enters, destroy target creature an opponent controls that was dealt damage this turn or has a -1/-1 counter on it.

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

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

This spell costs {1} less to cast for each creature that attacked this turn.

Other Warriors you control get +2/+0.
Whenever a Warrior you control dies, Bloodshed Devotee deals 1 damage to target opponent.

Discard a card: Bloodshot Berserker gets +1/-1 until end of turn. Any player may activate this ability.

When Bloodsoaked Blades enters, creatures you control get +2/+0 until end of turn.
Equipped creature gets +1/+1.
Equip {1}

Creatures you control that have been dealt damage this turn get +2/+0.
When Bloodspawn enters, it deals 1 damage to target creature you control.

Enchant land
Enchanted land has “{T}: Each opponent loses 2 life.”