Where is the gem that u need to find in the sewers??????

The only important gem I know of is the one that is on an altar in Mekrath's home, which has a sewer entrance. The gem is needed by a Haer Dhalis quest who is given to you by Mekrath as a slave. Maybe too much info but that is the only important gem I know of in the sewer area.

Why do you think you need a gem? What quest are you doing?

Orliamar where are you from? The number of people who can't understand your questions (myself included) is quite funny. Is it a language thing?

I'm referring to the post where you were talking about an individual saved game, yet called it a character, but after my reply about characters said
"You don't understand, I'm not talking about a person, as in Aerie.."

We'd love to help but you need to communicate adequately bro.