Beckoning Will-o'-Wisp

Flying
Lure the Unwary — At the beginning of combat on your turn, choose an opponent.
Creatures attacking the last chosen player get +1/+0.

Breathless Knight

Flying, lifelink
Whenever Breathless Knight or another creature enters the battlefield under your control, if that creature entered from a graveyard or you cast it from a graveyard, put a +1/+1 counter on Breathless Knight.

Anafenza, Kin-Tree Spirit

Whenever another nontoken creature enters the battlefield under your control, bolster 1. (Choose a creature with the least toughness among creatures you control and put a +1/+1 counter on it.)

Bloodghast

Bloodghast can't block.
Bloodghast has haste as long as an opponent has 10 or less life.
Landfall — Whenever a land enters the battlefield under your control, you may return Bloodghast from your graveyard to the battlefield.

Akuta, Born of Ash

Haste
At the beginning of your upkeep, if you have more cards in hand than each opponent, you may sacrifice a Swamp. If you do, return Akuta, Born of Ash from your graveyard to the battlefield.

Basilica Bell-Haunt

When Basilica Bell-Haunt enters the battlefield, each opponent discards a card and you gain 3 life.

Blessed Spirits

Flying
Whenever you cast an enchantment spell, put a +1/+1 counter on Blessed Spirits.

Belfry Spirit

Flying
Haunt (When this creature dies, exile it haunting target creature.)
When Belfry Spirit enters the battlefield or the creature it haunts dies, create two 1/1 black Bat creature tokens with flying.

Arashi, the Sky Asunder

{X}{G}, {T}: Arashi, the Sky Asunder deals X damage to target creature with flying.
Channel — {X}{G}{G}, Discard Arashi: Arashi deals X damage to each creature with flying.