A Distraction
The assault had been going rather poorly, but the human forces were doing better than could have been expected. Though the beastman soldiers were individually stronger and had more unit cohesion, the fact that the entirety of the human army was all Marked Ones gave them some advantages.
The biggest one is that marks were about as varied as the people themselves. Some had abilities as mundane as creating a water spout, or lighting a campfire. While others had grand abilities that healed major wounds or cracked the very earth beneath them.
This massive variation between every one of their soldiers made the enemy cautious, and being overly cautious was just as dangerous as being ignorant of the danger. They both led to mistakes.