King of the Oathbreakers

Flying
Whenever King of the Oathbreakers or another Spirit you control becomes the target of a spell, it phases out. (Treat it and anything attached to it as though they don't exist until your next turn.)
Whenever King of the Oathbreakers or another Spirit you control phases in, create a tapped 1/1 white Spirit creature token with flying.

Soldier of the Grey Host

Flash
Flying
When this creature enters, target creature gets +2/+0 until end of turn.

Fog on the Barrow-Downs

Enchant creature
Enchanted creature is a Spirit and can't attack or block. (It loses all other creature types.)

Apothecary Geist

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

Shadow Summoning

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

Oath of the Grey Host

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — You and target opponent each create a Food token.
II — Each opponent loses 3 life. Create a Treasure token.
III — Create three tapped 1/1 white Spirit creature tokens with flying.