Get "a tiny note" by clicking a crate in the basement of Nektropos Castle ( -15, -13, -32 ) /waypoint -15, -13, -32. Quest starts by examining the note.
Go to the basement under Elise's Bedroom. Use the lamp to open the wall. Billy should spawn as you enter. Kill him. ( 49, 0, 75 ) /waypoint 49, 0, 75
Go to the Game Room and walk into the room, Billy will now auto-spawn when someone is on this step of the quest.
Go to the the Chapel. Again Billy auto-spawns when you walk into the room now.
Go to the Library. Read a book in the secret area behind the bookcase. It's the book leaning against the coffin at ( -23, 13, 29 ) /waypoint -23, 13, 29. It's written by Everling and he says, "the dolls I need always come to me in the courtyard".
Go down to the courtyard by the entrance. A NPC version of Billy will spawn automatically. Hail him. The dialogue gives you two options, either give him 5g or yell at him. Give him gold.
Go to the jail and hail the froglok ghoul assassin ( -24, 0, 29 ) /waypoint -24, 0, 29. He tells you to get something to soothe his soul.
Go to the library and read the directions on a scroll ( -22, 13, 31 ) /waypoint -22, 13, 31 in the hidden area. (see sub-step 3 before leaving the library)
Kill 21 Nyth dolls. 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.
Fiendish blood: This is a triggered 35^^^ Lamia which will probably aggro you as soon as you leave the library or shortly thereafter. So be ready.
Go back to the froglok assassin and speak to him. He depops at the end of quest conversation. If everyone finishes at the same time you're okay, if not just wait ten minutes for him to repop. So try to time your hailing so that you all do it at once.