The Theban Triad (Side Quest)
Find this one by speaking to priestess on the west end of the Temple of Karnak (in the north of Thebes).
She sets you to investigating the theft of holy idols. Head back into the temple eastward, to enter an investigation area where people are making offerings.
Follow the trail of gold-marker breadcrumbs up the south wall to some coiled rope.
Then over the wall, following the blood trail from the broken ladder to the hapless thief.
He gives up his employer. Follow your marker into Thebes, then use Senu to identify the three malefactors, lurking next to a tiny pond, across the street from a small shrine.
You don't need anyone alive here, so take them out as you like.
You now have three new objective points along the Theban waterfront, one for each idol. For the northmost, search inside the ox carcasses. Don't worry about the screenwarping stench, that's normal.
The next one, as you work your way south, can be found inside a forge's fire.
The last is underwater, but you may want to snipe the nearby hipppos before venturing out for it.
With all three in hand, go seek out the priestess again. She has left the Temple of Karnak, and is now in the black market- speaking with her completes the mission.