It was the door.  Oh, and a flame elemental.

 

See, Asmodean was a video game fanatic when he was younger, and played Ultima Underworld: The Stygian Abyss.  In that game, there is a wizard who turned himself into a door, so that people would leave him alone and he could spend his time thinking.  But he got mad any time someone opened him, because it disturbed his thinking.  So, when Asmo opened him (he was in Caemlyn on interdimensional vacation) he took Asmo back to the Stygian Abyss with him.

 

Now, Asmodean would have recognized him from playing the game when he was younger.  And he would have known that nobody could get out of the Stygian Abyss, because the door only opens on one side (unless the volcano erupts ... but thats another story).  So he was stuck (which is how his location prevented the Dark One from bringing him back ... even Shai'tan can't get into the Stygian Abyss).  Then a fire elemental hit him in the back with a fireball (see, a lava stream runs along the floor near that door in the game ...)

 

Yeah.  Thats it all right.

And he would have known that nobody could get out of the Stygian Abyss, because the door only opens on one side (unless the volcano erupts ... but thats another story).

 

~nodding~ 

 

This all makes sense to me now.