OK, so I glanced over The Head info again, and it seems to me that most of it points toward it working for The Deceiver--perhaps being nothing more than a mouthpiece and magical conduit. First of all, considering the actions The Head takes:
It reveals Shiver's weakness, enabling her destruction. We know that The Deceiver and Shiver are old enemies.
It helps the Light retrieve the Total Codex. Now, as others have pointed out on the forum, we don't really know why this was a huge deal--the narrator never mentions the Nine discovering anything amazing in the Codex. But we *do* know that The Watcher was already looking for it, and we know that Myrdred would take any opportunity to sabotage one of Bahl'al's missions. Especially since exactly the same thing happens in The Black Company.
It reveals that the Dark has learned how to use the World Knots, and has a part of the Legion sent to destroy one Knot. Now this is a setback to the Dark in general, but probably affects the Deceiver less than other Fallen Lords, since he can teleport unaided. Also, since The Deceiver's armies are trying to cross the Cloudspine on foot at this time, it's likely that it's another Fallen Lord who plans to send forces through the Knot. Finally, the soldiers who have to go and destroy the Knot are--as the narrator explains in his journal--therefore unable to meet up with the main army which is marching to block The Deceiver's advance. So tipping off the Light about the Knots means that they can't give The Deceiver their undivided attention.
It has Alric sent across the mountains, where--surprise, surprise--he's promptly captured by The Deceiver. Once Myrdred's turned Alric over to Balor and gotten his props, it probably (this is is a suspicion of the narrator) informs The Nine so that a rescue attempt can be made.
It probably (the narrator doesn't know how they figured it out) tells The Nine about The Watcher's arm. The Deceiver has been digging for the arm for months now, and when the Light forces get there, they find the arm conveniently sitting on the ground. As soon as they go for it, The Deceiver starts attacking and tries to get it back. It's hard not to suspect that Myrdred just needed to be able to blame the arm's reappearance on the Light, so that the rest of the Fallen wouldn't realize he was working toward Bahl'al's demise yet again.
It starts a civil war and gets some of the Nine killed. Of course, any of the Fallen would want this.
Now, as for The Head's general character and abilities:
It apparently possesses powerful mind-control magics, which can persuade thousands of soldiers to fight for it, or turn the Nine into gullible idiots. We all know who the master of mind control is.
It never takes any physical action (though all it could really do is spit, I guess), but rather manipulates others through judicious application of truth and lies. This is Myrdred's M.O.
It claims to be an Avatara of Connacht's time, and a close friend or ally of Connacht. This is, so far as we know, exactly what Myrdred was. If The Head's relaying info from Myrdred, it'd make sense for it to validate that info by borrowing an edited version of Myrdred's life story.
It disappears entirely following the civil war. This is less surprising if it's just a tool or a mouthpiece than if it's an independent entity.
I wonder if earlier versions of the TFL story spent more time on The Head's betrayals, or on those of whatever creature controlled it? The biggest subplot of the first Black Company book is Soulcatcher's systematic annihilation of the rest of the Taken; perhaps TFL started out focused on this, and then moved away from the Black Company model (as it did with Shades) once it really found its individual flavor.
--SiliconDream
