I suspect though that, considering Taim's position as the leader of one of the most powerful dark friend factions (about 100 male channelers follow him - Taim and his dark 100 anyone?), that he is important enough to swear at the Pit of Doom. If he hasn't done so already.

Osan'gar was planted in the black tower, but was he there to keep an eye on the black tower and Taim or to watch Rand?