Velothi Tower thats now home to a mad alchemist and their bodyguards who are juiced on potions.
Should have some cells for prisoners and a lab for experiments, make sure to include lots of fortify potions and play around with pipes and the like to really sell it as a mad science lab.
A large Kwama mine on the edge of the Coronati basin, direct most of the size downwards, include some water pools in the lower levels and some acid pools closer to the wueens chamber.
(Lower-level questline, here to introduce general Narsis district themes surrounding Legion-Hlaalu relations, with an emphasis on tensions between the Hlaalu and Redoran -- ideally, Hlerynhul will be a place the player can join the Legion.)