Pax Romana (Side Quest)
This late game quest is available only after you have completed the Absolute Power, One Bad Apple, and Playing With Fire sidequests. This is where you finally assemble the triumvirate that the Oracle of Apollo spoke of.
Start by speaking with Diocles in Cyrene.
He needs you to find some paperwork in the Akropolis- it's being stored in the same underground chamber beneath the commander's quarters as one of the location treasures. As before, slip into the Akropolis by climbing up the northmost brazier tower.
Descend to the ground via the nearby privy.
Enter the commander's quarters through the window, and go to the southern room for a ladder down.
Take the scroll from the wooden table in the underground chamber.
Retrace your steps to Diocles, and speak with him to pass on the deed.
Diocles gives his thanks, and news that Vitruvius has been attacked on the road. Ride to the rescue.
As advance scans show, there are no hostiles on site by the time you arrive.
Speak with Vitruvius, who's magnum opus has been stolen by bandits. Track them down to the Desperate Gully Hideout.
The camp itself is a round depression- captain and treasure on one side, the Pax Romana objective on the other (it's being carried by a bandit, so will wander about slightly. Same goes for the captain, really).
Come in from the top, sniping any sentries that look like they might interfere.
Shadow the manuscript-keeper from above, until you can drop down on his platform and end him.
This gives you the manuscript.
Keep to the heights as you head to the treasure. The cave here is guarded, but the sentry will wander off from time to time, give you a clear in.
Loot the red chest inside for the local treasure.
The captain is quite the rambler, walking around camp and up and down platforms. Shadow him until you have killing solution.
His death ends the location.
Vitruvius is back in his aqueduct camp- speak to him there to return the manuscript, and arrange a meeting.
Now return to Balagrae, and speak to Praxilla for the third leg of this quest.
Crios, the waterbearer you took from the Temple earlier, has gone missing. Use Senu to track him down.
He's surrounded by attacking lions, but you've killed empires. Dispatch the beasts.
Speak with Crios, then meet up with your friends at the Oracle of Apollo.
Speak with them to complete the quest.
You also get a rare bow, for some unrelated reason.