Pavilion of Judgement (Heb Sed)
A stelae location in Heb Sed. You'll pass by the area during the Follower or Leader side quest.
The stelae is in the back (southerly) cavern part of the camp.
As usual, shrubs and ledges are the best tools for a steealthy approach, the the cavern is open enough that you'll probably want to engage in some preventative slaying before making for the tablet itself.
When the area is secured, read the stelae to get a riddle fragment and complete the location.