Quicksand

{T}: Add {C}.
{T}, Sacrifice Quicksand: Target attacking creature without flying gets -1/-2 until end of turn.

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.)

Plains

Gather the Townsfolk

Create two 1/1 white Human creature tokens.
Fateful hour — If you have 5 or less life, create five of those tokens instead.

Lumithread Field

Creatures you control get +0/+1.
Morph {1}{W} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Soul Warden

Whenever another creature enters the battlefield, you gain 1 life.

Raise the Alarm

Create two 1/1 white Soldier creature tokens.

Journey to Nowhere

When Journey to Nowhere enters the battlefield, exile target creature.
When Journey to Nowhere leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Soul's Attendant

Whenever another creature enters the battlefield, you may gain 1 life.

Ramosian Rally

If you control a Plains, you may tap an untapped creature you control rather than pay this spell's mana cost.
Creatures you control get +1/+1 until end of turn.

Guardians' Pledge

White creatures you control get +2/+2 until end of turn.

Squadron Hawk

Flying
When Squadron Hawk enters the battlefield, you may search your library for up to three cards named Squadron Hawk, reveal them, put them into your hand, then shuffle.

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. (They can't be blocked except by creatures with flying or reach.)