This is a level 8 side quest located in the Temple of Sekhmet in Yamu in Lake Mareotis region (reached immediately after you turn back from Animus for the first time). This is a pretty straight-forward quest and does not need any explanations but it has pre-conditions: You have to finish "Ambush in the Temple" and then "Ulterior Votive" side missions (level 6 and 7), which are also located in the temple.