Ghostly Fireball
Version 0.19: This article may not be up to date for the latest stable release of Crawl.
Ghostly Fireball is a monster-only spell which behaves much like the Fireball spell, dealing heavy, unavoidable damage to everything caught in its 3×3 blast radius. Unlike Fireball, however, it deals partially-irresistible negative energy damage, ignores half of its victim's AC, and heals any undead affected by it.
The following enemies cast Ghostly Fireball:
- z
Antique champion (3d24 damage) - L
Josephina (3d25 damage) - @
Josephine (3d15 damage) - z
Revenant (3d22 damage)
Additionally 6 
Blood saint's Legendary Destruction spell can result in a ghostly fireball.
History
Ghostly Fireball was added in 0.13.
