Altamont Ravenard
Explorer
Desperation?
Being struck stupid by fear? (really scared people don't always make smart choices, right?)
A scared person might kill himself to avoid being tormented by the demon. A scared person might fall down and cower. A scared person might flee. A scared person might try to play dead. A scared person might step back and hide behind its shield/weapon(s). I can't conceive (maybe only by my fault, and I'm usually an open-minded DM) a plausible reason for a character, faced with a dire foe and on the verge of death, to hit himself on the head with the hope of falling unconscious so that the demon facing me would instantly forget about disemboweling me and direct its attention to one of my comrades.
As a DM, assuming I would have thrown a Vrock against a 4th-level party, I would have let the player try the action, imposing some sort of penalty or will save for self-mutilation, or suggested that the character tried to play dead. If the player actually attacked himself, succeeding or not in knocking himself out, the Vrock would still have made an attack against the character (it's not a stupid creature [Int 14 in the 3.5 SRD]), but certainly not a coup de grâce.
Another action, as a DM, that could have made the Vrock change target would have been for the character to (truthfully or not, either way some sort of Diplomacy or Bluff check would have been in order) pledge his life to the Vrock and start attacking his (once) allies.
BTW, shouldn't justifications for a PC's action come after the fact? Prior to/as an act being performed, the only justification needed is the player stating "my guy does x". It's after the fact when the player, if not the group, may need to pay lip service to the character's internal motivations so as to preserve the illusion of a believable world.
How could motivation come after the act? How could the cause come after the effect? I don't want to argue from a hardcore simulationist position, but if I want my character to do X, I should have a reason for this action. If not, then why the heck did I attempt what I just did?
A player stating "my guy does X" is not motivation, nor justification for the character's action. It is the action.
AR