All of these ideas seem to say that the head either vanished or was defeated by the avatara. How unimaginative ;). Here's my theory, but it probably won't work out quite right, but here goes.
First of all, the winning endgame pics of Deceiver, Summoner, and Murder of Crows show the deceiver wielding something that is not his scepter. In all other pictures of the deceiver, he is holding a scepter with a head MOUNTED on it. In these three picture the top of the head is being penetrated by the top of the stick, and the stick itself is much smaller than the other.
The deceiver is crossing the stair of grief, where he meets up with a group of people who are under the influence of the head, and carrying the head with them. Our favorite Fallen lord knows this quite well, and like all evil guys wants more power. What better way to get power than to control such a powerful entity. After a nice long battle with the head, the deceiver ends up with a charred nasty skull which he promptly skewers with a handy stick, and enchants so that it will help him.
Soon a warlock arrives and tells Myrdred that there is an Alric approaching. The deceiver figures that if alric is here, it must mean he killed balor (Alric is the only remaining avatara, and since D just lost a bunch of his power, something must be up). D know's he's not going to be able to win, having just used up all of his major energy on the head, so he hides his new scepter away where only he can find it, and whips out his old one, does battle with Alric, and is imprisoned.
60 years later he's awakened, and has one of his locks dig up his newer scepter and get it to him. He hides this scepter with some magic. Alric knows the old scepter, because he had been captured by D in TFL during the hero missions. The D knows that Alric knows, and makes sure Alric never sees his cool new scepter, which he uses whenever Alric's around.
As we can see from the win screen of Murder of crows, the D beat SB with the Head scepter, and in the end of Summoner he cracked the summoner up with the Head also.
There ya have it. feel free to worship this idea :)
