Breath of the Sleepless

You may cast Spirit spells as though they had flash.
Whenever you cast a creature spell during an opponent's turn, tap up to one target creature.

Mental Journey

Draw three cards.
Basic landcycling {1}{U} ({1}{U}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Essence Flux

Exile target creature you control, then return that card to the battlefield under its owner's control. If it's a Spirit, put a +1/+1 counter on it.

Dreamshackle Geist

Flying
At the beginning of combat on your turn, choose up to one —
• Tap target creature.
• Target creature doesn't untap during its controller's next untap step.

Spectral Arcanist

Flying
When this creature enters, you may cast an instant or sorcery spell with mana value less than or equal to the number of Spirits you control from a graveyard without paying its mana cost. If that spell would be put into a graveyard, exile it instead.

Geist of the Archives

Defender
At the beginning of your upkeep, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Drift of Phantasms

Defender (This creature can't attack.)
Flying
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Fogwalker

Skulk (This creature can't be blocked by creatures with greater power.)
When this creature enters, target creature an opponent controls doesn't untap during its controller's next untap step.

Dungeon Geists

Flying
When this creature enters, tap target creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control this creature.

Cemetery Illuminator

Flying
Whenever this creature enters or attacks, exile a card from a graveyard.
You may look at the top card of your library any time.
Once each turn, you may cast a spell from the top of your library if it shares a card type with a card exiled with this creature.

Island

Mausoleum Wanderer

Flying
Whenever another Spirit you control enters, this creature gets +1/+1 until end of turn.
Sacrifice this creature: Counter target instant or sorcery spell unless its controller pays {X}, where X is this creature's power.

Catlike Curiosity

Enchant creature
Enchanted creature has "Whenever this creature deals combat damage to a player, draw a card."
If Catlike Curiosity would be put into a graveyard from anywhere, exile it instead.

Mischievous Catgeist

Whenever this creature deals combat damage to a player, draw a card.
Disturb {2}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Mischievous Catgeist // Catlike Curiosity

Counterspell

Think Twice

Draw a card.
Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Sleep

Tap all creatures target player controls. Those creatures don't untap during that player's next untap step.

Geistwave

Return target nonland permanent to its owner's hand. If you controlled that permanent, draw a card.

Spectral Prison

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.
When enchanted creature becomes the target of a spell, sacrifice this Aura.

Rattlechains

Flash
Flying
When this creature enters, target Spirit gains hexproof until end of turn.
You may cast Spirit spells as though they had flash.

Nebelgast Herald

Flash
Flying
Whenever this creature or another Spirit you control enters, tap target creature an opponent controls.

Hidden Strings

You may tap or untap target permanent, then you may tap or untap another target permanent.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Geistlight Snare

This spell costs {1} less to cast if you control a Spirit. It also costs {1} less to cast if you control an enchantment.
Counter target spell unless its controller pays {3}.

Skyline Cascade

This land enters tapped.
When this land enters, target creature an opponent controls doesn't untap during its controller's next untap step.
{T}: Add {U}.

Spectral Sailor

Flash (You may cast this spell any time you could cast an instant.)
Flying
{3}{U}: Draw a card.

Latch Seeker

Castle Vantress

This land enters tapped unless you control an Island.
{T}: Add {U}.
{2}{U}{U}, {T}: Scry 2.

Supreme Phantom

Flying
Other Spirits you control get +1/+1.

Unsubstantiate

Return target spell or creature to its owner's hand.

Hands of Binding

Tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)