Flayed
Version 0.13: This article may not be up to date for the latest stable release of Crawl.
Flayed is a status effect which can be inflicted on you by flayed ghosts. Each time you are flayed, you'll see your HP drop by moderate amount which is proportional to your max HP; getting hit by it multiple times will increase the amount of flayed damage (but can never reduce you below 35 HP) and reset the effect's timer. This damage can be healed through normal means, and attacks which reduce you to 0 HP after being flayed are lethal, but the flayed damage itself is illusory; all such damage will be immediately healed the moment you kill the flayed ghost or spend enough time out of its line of sight.
History
Flayed was added in 0.13.