Regarding the tusks I would go with one of two thoughts. First, simply that it is somehow a manifestation of his soletaken form. To be honest I can't remember everything from either instance, but both Spite in BH and Rake in TtH are described as having elements of their draconic forms while remaining somewhat humanoid. Slightly offtopic: If this state is common or represents control based on proficiency it might help explain Ryllanderas' seemingly inconsistent form.
Second is that it's his natural form if he is indeed an elemental or primordial elder god. There is definitely evidence supporting that possibility. I really can't remember the book or the instance exactly, but Osserc appears to be old enough to be recognized as a dangerous force by Draconus while Draconus still felt Rake was an upstart. While we really don't know much about the origins of the universe or the Tiste, the mythologies do seem fairly consistent in making the Andii older than the Liosan, and certainly not any younger. In this situation Osserc being an Elder God would certainly explain Draconus' position.
As for his power it would seem he is comparable to Rake in overall power although several comments from Gothos or Mael seem to imply that Rake tended to prove himself the more effective individual.
We know from several elder characters and even L'oric that Osserc is not an easy being to get along with and that he is normally either being supremely arrogant or aloof to the point where he seems to be.
While I don't quite understand his role in RotCG, I don't think it conflicts all that much with his appearance earlier. Both Osserc himself and the Queen of Dreams seem to indicate that he has spent a great deal of time sleeping. While perhaps not as potent as Burn's slumbering he appears to be quite busy during his sleep. If I remember correctly he is researching something, the KCCM maybe, but I don't know just how his dreaming world works, whether it actually involves a form of time travel or if he is simply working with a tangible "echo" of sorts.
His interaction with Cots, ST and Traveller seems fairly consistent on several levels. First he is Osserc, someone we are told several times is quite difficult to get along with and self centered. He is also either an elder god, or just very very old. In either case most examples of either of these possibilities frequently appear extremely overconfident, even when it seems they should be able to roughly judge the power of their opposition. I don't know how long Osserc his been "gone", but if what we are lead to believe is true and that Cots, ST and Traveller are all new players in the grand scheme of things then he may simply be ignorant of their true potency.
That said, I'm not sure how far the ignorance thing can go, when Icarium, with chronic memory loss, is still able to determine that Traveller was possibly powerful enough to kill him, by simply visiting Drift Avalii sometime after Traveller left it in BH.
Edit: Seems I was a little late on a couple of those points. Also, I've seen a reference or two to spoilers, but I would think anything except DoD and MAYBE TtH would be fair game in this forum.
This post has been edited by The Deragoth: 09 September 2009 - 02:48 AM