if you look back through this ooc thread you should find lots of history stuff, on the page before this i provided info for our other new player Ion. so most of that will cover you.
since you like option 2, lets go with that one. reasons for you being in the sewer could include: a really bad night that you dont remember much after you started drinking; on the trail of someone or something;
actually that second one sounds best. lets say that someone close to you was murdered in Sormere (a city a few weeks by ship to the south). You have been trailing the murder and clues have led you here to Ao Manasa. There is a group of thieves and hired killers called the Gloomblades who have connections here, particularily to a local crime boss by the name of the Hydra. Rumors around the city seem to point to ties between this Hydra and a man known as the Scrig King. As the Hydra himself has been difficult to track you have had to follow things on the way up the chain of command. So you are searching for this Scrig King and what better place than where most of the scrigs are said to hang out ~ the sewers.
If a murderer is not really in your vision of your character, then perhaps this Hydra is said to have an item in his possession that your character covets.