Millicent, Restless Revenant

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

Spell Queller

Flash
Flying
When Spell Queller enters, exile target spell with mana value 4 or less.
When Spell Queller leaves the battlefield, the exiled card's owner may cast that card without paying its mana cost.

Drogskol Reaver

Flying, double strike, lifelink
Whenever you gain life, draw a card.

Selfless Spirit

Flying
Sacrifice Selfless Spirit: Creatures you control gain indestructible until end of turn.

Tradewind Rider

Flying
{T}, Tap two untapped creatures you control: Return target permanent to its owner's hand.

Keening Apparition

Sacrifice Keening Apparition: Destroy target enchantment.

Geist of Saint Traft

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Whenever Geist of Saint Traft attacks, create a 4/4 white Angel creature token with flying that's tapped and attacking. Exile that token at end of combat.

Spectral Shepherd

Flying
{1}{U}: Return target Spirit you control to its owner's hand.

Drogskol Captain

Flying
Other Spirit creatures you control get +1/+1 and have hexproof. (They can't be the targets of spells or abilities your opponents control.)

Sturmgeist

Flying
Sturmgeist's power and toughness are each equal to the number of cards in your hand.
Whenever Sturmgeist deals combat damage to a player, draw a card.