Soris Arenim is a dunmer commoner living with his wife Erissare Arenim in the Imperial City. He has a penchant for mage's staves and is friends with Ulen Athram.
He hardly leaves his house and fortunately for him so dose his wife. During the Bravil recommendation quest you will need to get him to part with Ardaline’s staff or steal it. Depending on how it was obtained the locals can be heard talking about it:
"Soris Arenim sure seems upset. I think he lost something important."
"I heard that Soris Arenim made himself quite a bit of money recently. He seems very happy about it."