Shards From a Star
This quest begins during the The Setting Sun story mission- Gamilat gives you the beriddled Scroll of Thoth that kicks this off.
The riddle of the Scroll of Thoth leads you, unsurprisingly, to the Temple of Thoth. Knock away some roots nears the base of the giant courtyard tree to claim a crystal from a carving.
Place the crystal atop the Thoth obelisk.
Two beams will shoot down to the corridor, regardless of time of day (though time of night is a different matter).
The beams lead to tiltable mirrors. Each mirror should be adjusted so that beam strikes the statue headpiece closest to the door (ie the north mirror should aim at the southmost of its three statues, and vice versa). You will have to burn the cobwebs off the the statue on the north side to make this happen.
This opens the passage under the tree.
Follow the passage and pick up the (quite nice) twin blades to complete the quest.
Note that there are other lootable down here, including some carbon crystals through a smashable wall. Watch out for snakes.
