Like the other side quests in Elden Ring, Millicent’s side quest can be a bit obtuse at times if you aren’t sure what to do next. After completing the first section of her side quest, which involves finding her in Caelid and curing her of scarlet rot, players will eventually reunite with her in the Altus Plateau. Players can find her at the Erdtree Gazing Hill Site of Grace, where she says she would fight alongside you if she only still hand her sword arm. Now you need the Valkyrie’s Prosthesis.
Head north to the Shaded Castle
From the Erdtree Gazing Hill, you want to head straight north, to the green swamp on the map. Here, you will find the Shaded Castle and the Valkyrie’s Prosthesis. As you might have guessed from the green sludge on the map, the castle is located in the middle of a poison swamp. It is also filled with enemies that will inflict you with Scarlet Rot, so come prepared with remedies for both of those. There is a Site of Grace in the southeast corner; once you enter the castle grounds, you will want to hit.
From there, head to the center portion of the swamp area, west from the site of grace. There will be a ladder there. Take that up, so you enter the castle itself. From here, you want to head up to the northwest part of the castle. There is another ladder near the first one, off to the left. Continue heading up and northwest. You will end up facing multiple Scarlet Rot Knights, will the Valkyrie’s Prosthesis in a chest. Return to Millicent at the Erdtree Gazing Hill and give her the arm. This will have her advance to the next location of her quest.
