Kill 21 dolls of Nyth; see monster article for locations. There are only 30 dolls in the castle and they do not respawn, so make sure you don’t kill them before you need them.
Kill the doll controller, Marionette of Nyth, an uncommon spawn at either ( -51, -13, -53 ) Copy/waypoint -51, -13, -53 or ( -19, -13, -31 ) Copy/waypoint -19, -13, -31. (Note: Doesn't always spawn. Might need to turn off merc/familiar if mentoring? Spawned the first time I did that after several non-spawns...was chrono'd to lvl 30)
Use the key on the box in the Quarters of Lord Everling, at ( 22, 12, -51 ) Copy/waypoint 22, 12, -51.