Royal Guards Rest (Heb Sed)
A stelae location in Heb Sed.
This stelae is little more heavily guarded than the other. You can approach the cavern unseen by hopping from pillar to pillar in front of the entrance.
A ledge on the south side will lead you into the cavern itself, where local ropes and spars give you some maneuvering room.
It is possible to drop down and read the stelae unseen, but a few strategic snipes or drop kills beforehand can make it much safer.
Either way, reading the stelae itself grants a riddle fragment and completes the mission.