well if you were a bio just use fully powered disrupt (2/2) knock out his focus then he will use a move that recovers it but he loses health. Just disrupt until he is dead.
Anyways, as psychological, you have the hardest lot of the three. Cast Haunt at beginning of battle, that way every turn the Baron loses 5 focus. Then cast traumatize as often as possible, as traumatize will make the baron lose 15 focus per turn for 2 turns. Do that until he's at 0focus, at which point he will hurt himself a lot to regain focus. Once his regaining focus stage is over, repeat with the traumatize (and haunt if neccesary), rinse and repeat till holy scars appears. When holy scars appears on baron, just hit him with your strongest attacks.
