Brutal Stuffsies is an achievement that requires the player to open Uglug's Stuffsies by giving Uglug Nar a relicym's balm.
If making the potion by themselves, the player will have to first talk to Sithik Ints and ask him "How do I get rid of the disease?" before being able to make the potion. They must do this before Uglug Nar will accept the balm.