To investigate Khaliset’s lair to uncover her whereabouts in The Hyena in Assassin’s Creed: Origins free and talk to the prisonor at the entrance of the the lair. Go towards the back of tha lair and into a cave and interact with the message on the rock and the sleeping area. Go back to the entrance of the lair and free the hyena. Kill it and go into the cage and interact with the back wall. .

As found on Youtube