Cast Ghostly Dancers by paying its mana cost.
When Ghostly Dancers enters the battlefield as an enchantment due to Secret Arcade, it triggers, creating a creature token.
When the Spirit enters the battlefield as an enchantment due to Secret Arcade, Ghostly Dancers's second ability triggers, creating a creature token.
Repeat step 3.

Infinite creature ETB

Infinite creature tokens

Draw the game

Secret Arcade // Dusty Parlor

Ghostly Dancers

Cast Ghostly Dancers by paying its mana cost.
When Ghostly Dancers enters the battlefield as an enchantment due to Enchanted Evening, it triggers, creating a creature token.
When the creature token enters the battlefield as an enchantment due to Enchanted Evening, Ghostly Dancers's second ability triggers, creating a creature token.
Repeat step 3.

Enchanted Evening

Cast Screams from Within by paying {1}{B}{B}, attaching it to a creature with toughness equal to 1.
The creature dies as a state-based action due to having 0 toughness.
Ghostly Dancers and Screams from Within trigger.
Resolve the Ghostly Dancers trigger, creating a creature token.
Resolve the Screams from Within trigger, returning it from your graveyard to the battlefield attached to the creature token
Repeat from step 2.

Infinite creature LTB

Infinite death triggers

Screams from Within

Activate any number of creatures you control by tapping them, adding at least enough mana to unlock a locked Room you control.
Unlock any Room you control by paying its mana cost.
Ghostly Dancers' second ability triggers, creating a 3/1 Spirit creature token. 
When the Spirit enters the battlefield, Intruder Alarm triggers, untap all creatures.
Activate Marina by tapping it, locking the Room that was unlocked in step 1.
Repeat.

Infinite untap of creatures

Infinite mana creatures you control can produce

Infinite unlocking of Rooms you control

Room Enchantment

Marina Vendrell

Intruder Alarm

Activate Goblin Bombardment by sacrificing another creature that has an Aura attached to it.
When the creature dies, Cass triggers, returning an Aura that was attached to the creature from your graveyard to the battlefield attached to another creature you control.
When the Aura enters the battlefield, Ghostly Dancers triggers, creating a creature token.
Resolve the Goblin Bombardment ability.
Repeat.

Infinite creature sacrifice triggers

Infinite damage

Cass, Hand of Vengeance

Goblin Bombardment

Cast Traveling Plague by paying {3}{B}{B}, attaching it to another creature you control.
When Traveling Plague enters, Ghostly Dancers triggers, creating a creature token.
Activate Viscera Seer by sacrificing the creature Traveling Plague is attached to.
When the creature dies, Traveling Plague triggers, returning itself from your graveyard to the battlefield attached to the token created in step 2.
When Traveling Plague enters, Ghostly Dancers triggers, creating a creature token.
Resolve the Viscera Seer ability.
Repeat from step 3.

Infinite scry 1

Traveling Plague

Viscera Seer

Cast Rancor by paying {G}, attaching it to any other creature you control.
When Rancor enters, Ghostly Dancers triggers, creating a creature token.
Activate Phyrexian Altar by sacrificing the creature with Rancor attached, adding {G}.
Rancor triggers, returning itself from your graveyard to your hand.
Repeat.

Infinite storm count

Phyrexian Altar

Rancor

Activate Phyrexian Altar by sacrificing the creature with the Aura attached, adding one mana of any color.
Mazzy's second ability triggers, exiling the Aura and allowing you to cast it until your next turn.
Cast the Aura from exile by paying its mana cost, attaching it to any other creature you control.
When the Aura enters, Ghostly Dancers triggers, creating a creature token.
Repeat.

Aura Costing One Mana that Enchants Creatures

Mazzy, Truesword Paladin

Cast Lightwheel Enhancements either from your hand or from your graveyard by paying {W}, attaching it to another creature you control.
When Lightwheel Enhancements enters the battlefield, Ghostly Dancers triggers, creating a creature token.
Activate Phyrexian Altar by sacrificing the creature with Lightwheel Enhancements attached, adding {W}.
Repeat.

Combos with "Ghostly Dancers"