Sanctum Spirit

Lifelink
Discard a historic card: Sanctum Spirit gains indestructible until end of turn. (Artifacts, legendaries, and Sagas are historic.)

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.

Grey Host Reinforcements

Flying, ward {3}
When Grey Host Reinforcements enters, exile target player's graveyard. Put a number of +1/+1 counters on Grey Host Reinforcements equal to the number of creature cards exiled this way.

Damn

Destroy target creature. A creature destroyed this way can't be regenerated.
Overload {2}{W}{W} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

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.

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice Ghost Quarter: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Fog on the Barrow-Downs

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

Living Death

Each player exiles all creature cards from their graveyard, then sacrifices all creatures they control, then puts all cards they exiled this way onto the battlefield.

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.