Quest
Hall of Mirrors seal locations
Four seals
GameSpot's sigil guide places four Sage Sigils. The first is in the Paris streets near the Prison Tower and Joan, and it needs no traversal skill. The second is in the Main Hall Archives, upstairs, with a lever puzzle on the left. The third is in the Clock Tower at Mechanic's Ascent, beside a shortcut on the left. The fourth is in Notre-Dame's East Gallery and needs Smash, double jump, and a dash from the highest point of the giant organ, then a breakable floor on the east side.
At a sealed mirror, hold down to enter, strike the lock on the mirror, and clear the guards. Four broken seals free Eleanor of Aquitaine and open the Hall of Mirrors.
After the hall
Inside the fog, find The Temptress in Belmont Manor. Beating her clears the fog permanently. Eleanor is not collected there. Her arcana is in the Tomb of the Noble Queen, back in Holy Innocents' Cemetery. That last step is the Sage virtue.
What I ran into
I broke three seals and assumed the quest item was in the manor. The tomb was the actual hand-in. The page ends on that trip because it is the step I skipped.
Questions
How do I enter a sealed mirror?
Hold down in front of it, then break the lock and clear the room.
Which seal needs double jump?
The East Gallery seal in Notre-Dame. The Prison Tower seal does not need a special skill.