Ghost Mastery
| Tier I | Whenever you die, activate  Ectodrop. |
|---|---|
| Tier II | If you're in ghost form at the end of a stage, revive with 1 life. |
| Tier III | [4 Charges] While in ghost form, activate  Ectoplasm and increase the amount of lives you revive with. |
| Unlock I | Unlock I by scaring 5 living objects while in ghost form on Normal or above. |
| Unlock II | Unlock II by scaring 20 living objects while in ghost form on Normal or above. |
| Unlock III | Unlock III by scaring 50 living objects while in ghost form on Normal or above. |
The Ghost Mastery is focused on surviving fatal damagy by becoming a ghost, scaring away Strangers and Monsters for loot.
Strategy
As base, Ghost is a resilient mastery. Activating Ectodrop on death ensures that even if a player can take lethal damage, they can clinch stage completions with the few turns left in their status counter.
While in Ghost Mode, clicking on stranger and visible will spook them, having them flee and drop coins and items. In tandem with items that can Reveal monsters, or items that can extend Ectodrop's duration such as a 
Hourglass or 
Divine Timepiece, a player can spook away all the monsters on the board for their loot. Granted, players cannot pick up loot while in Ghost Mode.
With its second tier, Ghost's ability to clutch stage completions is rewarded with being revived at the end of the stage. This allows the Ghost to have lethal mistakes forgiven, and be able to collect all the loot gained from spooking.
A more aggressive way to use Ghost Mode is to nearly solve a stage, then die intentionally. With Ectodrop not being penalized by taking monster damage, this makes the player invulnerable for 30 turns. With each revealed monster taking only one turn off the timer, a player can reveal and spook several dozen monsters for their loot, before spending only a few turns to solve the stage.
This ability to wield Ectodrop's monster damage immunity can also feed into Ghost's ultimate ability: converting the Ectodrop counter into a newly stocked Ectoplasm, granting an additional 200 Cells of solving time for a given stage.
Ectoplasm is susceptible to monster damage, removing 10 Cells of solving time per damage dealt, balanced out by gaining additional counters by spooking Strangers and Monsters, +30 per haunted victim.
In tandem with Ectodrop revealing up to 29 Monsters and being left at 1 turn counter, using this ultimate and spooking those monsters can net the player an additional 870 Cells of solving power, for a total of 1,070 Cells to complete the given stage.
Changelog
- v2.27 (patch notes missing)
- Fixed Ghost III ultimate not reliably activating Ectoplasm while in ghost form.
- Updated Ghost III description for clarity. (was "Activate Ectoplasm and increase the amount of life you revive with.")
- v2.20 (patch notes missing)
- Ghost form buffed: While in ghost form, any object that flees might drop items, even if the flee is triggered by an item
- Ghost mastery unlock requirements changed from Ectoplasm counter to scaring objects in ghost form
- v2.00 (patch notes missing)
- Ghost II buffed: "If you're in ghost form at the end of a stage, revive with 1 life." (was "Whenever you complete a stage in ghost form, revive with 1 life.")
- Ghost form buffed: Strangers and monsters you scare away can drop loot.
- v1.88
- Ghost I nerf: "Whenever you die, activate Ectodrop." (was "Whenever you die, activate Ectoplasm").
- Ghost II rework: "Whenever you complete a stage in ghost form, revive with 1 life." (was "Whenever you complete a stage in ghost form, gain Scary Mask.")
- Ghost III rework: "Activate Ectoplasm and increase the amount of life you revive with." (was "Revive with 1 life.")