From the Basic Set, p.419:
Quote:
|
-10xHP – Total bodily destruction, if this makes sense given the source of the damage – 200 points of arrow wounds leave a messy but recognizable corpse; 200 points of fire injury leaves nothing but an unrecognizable lump of charcoal. The difference can be important in settings where resurrection, reanimation, etc. are possible!
|
That means that your corpse is
totally destructed. You can't act anymore, no matter how your HP came to be this low. You are not dead nor unconcious, but in effect, you don't have a body anymore.
Since you can't die and are conscious, your seat of consciouness is in your husk of "not-body". So, in order to kill you, someone must deal 1hp of damage from your weakness.
In other words: you can't act anymore, you can't have your hp lower than -10xhp, but you are still alive and conscious.