Creative

Working on a dungeon for my Pathfinder 1e game. Hidden in the sewers underneath the city is an underground complex of insane Derro (little halfling sized purple-skinned insane humanoids) who have been capturing people for their experiments. I have some fun encounters planned, and I intend to make them really weird and alien. Derro alchemists with sentient tumors, psychic malformed derro babies held aloft in golden cages and used as living war banners, mutated and mind controlled humans from the city above used as muscle and servants, fungus monsters, suicide-bomber homonculi, etc etc. I plan for the big reveal to be that a character they met previously (an elven alchemist who runs a free clinic in the city) to be the mastermind behind the derro lair. He's been buying slaves and experimenting on them for centuries (a la Nazi experiments during ww2) to further his medical knowledge which he uses to help people (and eventually cure death but thats mostly for him). He brought the Derro from the deep underground closer to the surface so he could guide their research towards something more productive (the Derros racial insanity makes it difficult for them to make any lasting progress). Oh also the Derro use their alchemical knowledge to wipe the memories of the people they experiment on before sending them back to the surface. Who knows how many hidden mutants are running around aboveground, and if the nightmares of the seemingly insane are actually resurfacing memories...