Vertigo
Version 0.21: This article may not be up to date for the latest stable release of Crawl.
Vertigo is a temporary status effect that decreases your evasion, spellcasting success, and accuracy until it wears off.
Vertigo is sometimes caused when casting Alistair's Intoxication, as a Hexes spell miscast effect (10+d11 turns), or when inside a cloud of seething chaos.
A potion of cancellation will remove the vertigo status (as well as many other status effects). Potions of curing have no effect.