Madiama
A one treasure, one captain camp in the far north of Arsinoe Nome
The camp takes up a box gorge, but you scarcely need to step inside to meet your objectives.
Come in from the eastern heights to get a bead on the captain.
Then drop down on the treasure guard (though you could also leave and come in through the 'hidden' passage).
Either way, loot the red chest in this cavelet (possibly disposing of one more guard) to complete the mission.