Anafenza, Unyielding Lineage

Flash
First strike
Whenever another nontoken creature you control dies, Anafenza endures 2. (Put two +1/+1 counters on it or create a 2/2 white Spirit creature token.)

Battleground Geist

Flying
Other Spirit creatures you control get +1/+0.

Apothecary Geist

Flying
When this creature enters, if you control another Spirit, you gain 3 life.

Abuelo, Ancestral Echo

Flying, ward {2}
{1}{W}{U}: Exile another target creature or artifact you control. Return it to the battlefield under its owner's control at the beginning of the next end step.

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.

Millicent, Restless Revenant

Affinity for Spirits (This spell costs {1} less to cast for each Spirit you control.)
Flying
Whenever Millicent or another nontoken Spirit you control dies or deals combat damage to a player, create a 1/1 white Spirit creature token with flying.