[Him]

I believe I intended for him to be sealed for about 500-800 years. That should be long enough so that only the elders would know and that would account for Sid's lack of knowledge on the subject. Probably Thauron is aware of him if he's in the right role to be taught some of the secrets of the elves.

So if Abaddon is feeling generous he'll allow Thauron in the group. But would he be willing to help them steal the information? Doesn't seem like it.