A soldier named Ash was not having a great day. Early into the battle, his powerful exoskeleton armor suit sustained damage to one of its knee joints. Although he could still fight and shoot his rifle, not to mention more than willing to face the abominations despite having his mobility severely reduced, the command judged that the risk was not worth it.
As a result, he had to abandon his fellow infantrymen and retreat to the supply train of the division, where a team of techs tried to repair his suit as fast as possible.
…Sadly, they weren't fast enough.
Who knew that a bunch of new Gates would open, with one of them appearing almost on top of the scarcely defended supply train?
While the techs and other non-combatants desperately tried to retreat closer to the main formation, Ash and a small number of soldiers that happened to be nearby had no choice but to face the advancing Nightmare Creatures alone.