The hero looks bad in this graphical style; he's supposed to be a demon, not a red knight. It's like demons have possessed the heroes of humans. Look at how different the heroes of different factions were in Heroes 5.

The canonical Inferno Hero: Knight of Hell (Might & Magic Hero)
This status is given to demon worshippers who have excelled in serving their master. Knights of Hell are not true demons, but Humans (Elves, Dwarves...), who have received "blessings" from Urgash and been "changed" by Chaos Magic.