Might be a dumb question, but is there a reason that Tiamat is included but not the good counterpart Bahamut?

Probably because Tiamat was needed for something, and Bahamut never came up as something needed. I think there was a group of players who started a dragon cult at some point.

Ummm oh. Any chance he can be added? I'll put the idea up as a good dragon cult prelude.

<removed -- don't post in other people's DM Q&A threads>

Bahamut has many other names, perhaps that confused you. Also, Tiamat is listed under human dieties due to his following in Chessenta. Bahamut is only listed under Dragon dieties, although he does have some human followers.

At least, according to: http://en.wikipedia.org/wiki/List_of_Forgotten_Realms_deities

Still, my question to the DMs is whether or not it can be permitted to have a cleric of Bahamut as a character, with the correct alignment (Lawful Good) and the correct domains (which are listed as Air, Cold, Dragon, Good, Law, Luck, Nobility, Protection and Storm). This was mainly important to fuel my prelude but since, as always, I didnt get any responses, its semi-less important. Still however, I would like to know if changes can be implemented to allow for it.