Battle Screech

Create two 1/1 white Bird creature tokens with flying.
Flashback—Tap three untapped white creatures you control. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Watcher of the Spheres

Flying
Creature spells with flying you cast cost {1} less to cast.
Whenever another creature you control with flying enters, this creature gets +1/+1 until end of turn.

Favorable Winds

Creatures you control with flying get +1/+1.

Rally of Wings

Untap all creatures you control. Creatures you control with flying get +2/+2 until end of turn.

Moorland Haunt

{T}: Add {C}.
{W}{U}, {T}, Exile a creature card from your graveyard: Create a 1/1 white Spirit creature token with flying.

Bygone Bishop

Flying
Whenever you cast a creature spell with mana value 3 or less, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Venerated Loxodon

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
When this creature enters, put a +1/+1 counter on each creature that convoked it.

Triplicate Spirits

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Create three 1/1 white Spirit creature tokens with flying.

Midnight Haunting

Create two 1/1 white Spirit creature tokens with flying.

Huntmaster Liger

Mutate {2}{W} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Whenever this creature mutates, other creatures you control get +X/+X until end of turn, where X is the number of times this creature has mutated.