I KNOW WHERE! Actually it is quite like an easter egg (a scary one to think about to be honest).
I was going to make a video about that but you will be privileged with the info right now :)
First go to the Magician Quarter and enter the Residential Area. The Residential area consists of this complex of residences with magician creatures.

Go to +1. The rooms at the north are with a nice Ice Witch. But the south area of the place contains Mad Scientists. Explore all of the south are of +1. In one of the Wardrobes, you shall find a dead body of a women. Nobody ever commented about that in Tibia as far as I know, but it looks kinda creepy to spot a dead woman inside of a room that is inhabited by male Mad Scientists... Anyway, I am not posting the image of the body or of the place because I am not with a Premium Time activated currently.
Reference of the map image used in my answer: https://www.tibiawiki.com.br/wiki/Magician_Quarter