lockpicked with a DC25 Sleight of Hand check, or with the spell Knock. However you open the wardrobe, you should then be able to pass through it to enter the secret room functioning as the killer’s hideout.
If you don’t haveall the Netherstones, the Emperor will warn you away from this area and reveal that this is where the Elder Brain was kept all along. Here, in the water, just below the city. If only to give the illusion that everything was under control when it most decidedly wasn...