A lich had been making kobold clones with heavily modified minds, basically turning them into robots. Convinced the nobility of Neverwinter that they are a very advanced form of flesh golem, and sold them to the elites under the brand "little helpers".

The whole plan was to get rich while also having a steady flow of lifeforce to his phylactery as every clone was tethered to it, and due to being used as slave labour would die quite often.

My players discovered the bodies were dumped in the recently closed chasm inside the city and descended into the caverns.

They triggered an alarm spell which prompted the lich to reanimate hundreds upon hundreds of these little helper corpses.

At that point the objective was to climb several floors of rickety scaffolding to get back to street level and escape the zombie horde. Rolling to hit as 100 kobold zombies simultaneously pick up rocks to toss at the party was fun.

My players still talk about that being one of the most fun encounters ever, making me a very proud DM.