In our last combat the party fought some Vampires. Initial I said they turned to Gaseous Form. After rereading the rules, it says turning into Gaseous Form is standard action, and under Fast Healing it says: "If reduced to 0 hit points in combat, it automatically assumes gaseous form and attempts to escape".
So does the Vampire turn immediate gaseous? Or is it, say, on its next action, which is now only a Move Action and then can start to float away?
And hence, is it possible to say use a wooden stake though the heart, if player has an action before the Vampire's next action?
If this is possible, is this a 'coup de grace' action that auto kills the Vampire, or is there some attack roll needed?