Hiya!
Well, there are RAW ways, sure...but for me death usually goes something like this:
DM (Me): You get clawed for [22] damage.
Player: Crap! I'm down.
Other Players: At least that bought us some time...
DM: The monster begins feasting on your unconscious body. At least you don't feel it. You're dead.
Player: Dang it...
Other Players: OK, so, we keep running, looking back to see if it's following us.
DM: Nope, no sign of it. Looks like the rest of you got away...this time...
In a nutshell...does it makes sense, world/campaign/setting sense (not necessarily rule-sense) for a character to be just outright 'dead'? If the answer is yes, I just inform the player his/her character is dead, regardless of how many HP's he had or didn't have. This is agreeable nine times out of ten. If the player and other players disagree, they give me their reasons, suggestions, or thoughts on why the character might live. Usually we go with my decision, sometimes with theirs, and other times we let the dice decide.
The point is..."realistic campaign consistency" trump rules every single time. My players would all MUCH rather have consistent, "logical" (game logic), than to never know if the DM was going to "let them live or not". And, honestly, just deciding "Yeah, well, uh, the demon stands over your body, victorious...and then, uh, leaves I guess..." is the same thing as saying "Oh, well, don't worry if you all hit 0 hp in this fight...he won't kill you if he wins, he'll just leave". Either way is the same thing as playing Tic-Tac-Toe against someone who always lets you win.
So...RAW, there are things that will kill a 10th level character....the DM just has to have the jewels to play the viciousness, alignment, and Intelligence of the enemies. Always. Ever time. Without compromise or malice. If the DM is neutral and fair, things almost always turn out for the best....sooo......always look on the bright side of life. Always look on the light side of life. If life seems jolly rotten, there's something you've forgotten, and that's to laugh and smile and dance and sing....When you're feeling in the dumps, don't be silly chumps!...just purse your lips and whistle, thats the thing! ...Sooo....
*ahem*
Fair. Consistent. Sensable from a campaign/story perspective is
always better than following the letter of the rules. IME, at any rate.
^_^
Paul L. Ming