Throughout DKS, we "kill" several ghosts in combat. Whether random enemies or named characters, they are nonetheless ghosts. So what happens to them when they're "killed" in battle, and they fall into the ground and vanish? Does this destroy their soul entirely, or does it force them into the Hall of Echoes (as opposed to allowing their soul to find the peace that bound them to the material world in the first place)?
Also, on this same topic, what happens to those killed in the Hall of Echoes? We re-battle several main nemeses in the arena there, but what happens to their souls?
And for the third question, what about demon souls in the Hall of Echoes? Razakel's line seems to imply that he can still transport himself (and others) to his home dimension of Tartarus, since he threatens that on you, although that may have just been wishful thinking on his part (since Laiken had his own fantasies he wanted to visit upon you).