This quest takes place in Eos. The reward is a shield spell.
Head north into Eos, and find 2 priests in Eos; each has a piece of the Crescent. Kill them and take their pieces.
Head east on Lunar street, to the end, and go down the ladder [down].
Go south, and take the SE branch, 2 south, two east, and pull torch to enter the temple.
all south and one west will get you to the priest who has the Crescent Top.
"assemble pieces"
Take path e, 3 north, east, south, east, up, west, south, southwest, north and enter "mirror 2"
2 south, and "place moon" to receive a 1-time Moon Shield (Shield Spell).