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.

Kami of Terrible Secrets

When Kami of Terrible Secrets enters, if you control an artifact and an enchantment, you draw a card and you gain 1 life.

Echo of Dusk

Descend 4 — As long as there are four or more permanent cards in your graveyard, Echo of Dusk gets +1/+1 and has lifelink.

Souls of the Lost

As an additional cost to cast this spell, discard a card or sacrifice a permanent.
Fathomless descent — Souls of the Lost's power is equal to the number of permanent cards in your graveyard and its toughness is equal to that number plus 1.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Screaming Phantom

Flying
Whenever Screaming Phantom attacks, mill a card. (Put the top card of your library into your graveyard.)

Sol Ring

Command Tower

Cleave Shadows

Creatures your opponents control get -1/-1 until end of turn. (Then exile this card. You may cast the creature later from exile.)

Shrouded Shepherd

When Shrouded Shepherd enters, target creature you control gets +2/+2 until end of turn.

Shrouded Shepherd // Cleave Shadows

Mondrak, Glory Dominus

If one or more tokens would be created under your control, twice that many of those tokens are created instead.
{1}{W/P}{W/P}, Sacrifice two other artifacts and/or creatures: Put an indestructible counter on Mondrak, Glory Dominus. ({W/P} can be paid with either {W} or 2 life.)

Call a Surprise Witness

Return target creature card with mana value 3 or less from your graveyard to the battlefield. Put a flying counter on it. It's a Spirit in addition to its other types.

Fog on the Barrow-Downs

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

Beckon Apparition

Exile target card from a graveyard. Create a 1/1 white and black Spirit creature token with flying.

Kaya, Intangible Slayer

Hexproof
+2: Each opponent loses 3 life and you gain 3 life.
0: You draw two cards. Then each opponent may scry 1.
−3: Exile target creature or enchantment. If it wasn't an Aura, create a token that's a copy of it, except it's a 1/1 white Spirit creature with flying in addition to its other types.

Unforgiving One

Menace (This creature can't be blocked except by two or more creatures.)
Whenever Unforgiving One attacks, return target creature card with mana value X or less from your graveyard to the battlefield, where X is the number of modified creatures you control. (Equipment, Auras you control, and counters are modifications.)

Searchlight Companion

Flying
When Searchlight Companion enters, create a 1/1 colorless Spirit creature token.

Moonshaker Cavalry

Flying
When Moonshaker Cavalry enters, creatures you control gain flying and get +X/+X until end of turn, where X is the number of creatures you control.