When Night Falls (Side Quest)
This Saqqara Nome side quest becomes available in Nitria, after completing the Rites of Anubis and First Blood sidequests.
Follow your marker to Suphia during the night time to launch this side quest.
Mount up and follow the NPCs. There's a lot of talk, but no encounters or ambushes.
You'll eventually arrive at Ekdikesis Outpost.
Dismount, and you'll all tend to your tasks. Bayek is assigned to carry three wounded men nearer the kiln (it's too bad stretcher technology seems as yet unknown here).
Lay down the last man in the designated area to trigger a cutscene.
This cutscene ends in an ambush by Roman soldiers. Fight them off.
The only notable enemy is the commander with the blue cloak and the tall shield. Try to flank him while he's fighting another opponent for an easy kill.
When all foes have been downed, Bayek is assigned to confront Suphia atop the brazier tower.
It's not really possible to sneak up on her- even if you do, it just glitches her dialogue.
Instead, climb the ladder and approach her normally to trigger a cutscene of rage and death.
This ends the mission.
It also grants Bayek a new mount.