The Hand of Merlin
54 Achievements
GOG
Warband
Unlock Prowess for every hero, while in Normal mode or harder.
0.8%
How to unlock the Warband achievement in The Hand of Merlin - Definitive Guide
Play through unlocking each character and then successfully completing a run on normal difficulty with that character alive throughout the whole run. If you are struggling with this then use two upgraded heroes and one normal hero and that should make it a lot easier to get through.