Brother-in-Arms | Demon's Souls Trophy
Vanquish Penetrator with Biorr
Location: 1-3 Inner Ward of Boletarian Palace
In order to vanquish the Penetrator with Biorr, you will need to rescue him first.
How to unlock his cell: His cell could be unlocked with the Iron Key Ring
This key will be dropped by a Fat Official. Once received, head back towards the entrance of the Tower Knight fight. On the right side will be a locked door.
Head down, defeat the Fat Official, and set Biorr free.
Let him sleep - and he will help you fight the Penetrator.