The Viziman Connection
Once you’ve cleared out the Salamandra in the Sewers from the quest Following the Thread, Jethro (#1) will give you this quest. The letter that you found from Gellert indicates that he has a post in the Sewers that acts as a Transfer Point (#2) for Fisstech.
Make your way to the Transfer Point and confront the Salamandra. There’ll be no discussion as they’ll attack on sight. Once you’ve killed them all loot the corpse of Gellert to find the Key to the Salamandra Code and a Royal Letter of Safe Conduct.
Head back to Jethro who should now be back in the Prison in the Temple Quarter and let him know what happened for your reward of 200 Orens.