When attempting to do prison breaks the archmages staff's special attack (the one that kills and has a really cool sound effect) doesn't work. It works perfectly on the field but not prison breaks (tried with Dirhim and another swadian castle and multiple bandit parties
).
Killing with flame arrow, black bolt, or archmages staff (on kill mode) produce duplicate damage and death messages, damage amounts are different but if they die it says two of the same unit died when only one did.
EDIT: Mercenary mages don't join in with the guards in stopping a prison break. Flame arrow seems to do nothing to swadian infantry and militia. I'm wearing archmage gear, with staff, healers ring, and a pair of elven plate boots (there appears to be no magic friendly boots so I went with the ones that looked like they would be). I got a headshot on swadian infantry while he was oblivious to the prison break and it did 0 damage, was only doing 4-6 damage on the militia.