User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-7584137-20140907101801/@comment-25119729-20140907104754

Wild animals using man made structures as a place to live is not that unusual. I guess the Fort stands most of time in the year empty, and is only used in emergencys. The stonewalls and it being a bit higher above the ground, it offers protection against any would-be-threats. Since the Canyon around it also seems to be pretty isolated, it could make a good birthplace for Iopreys. They come there to lay their eggs and raise the young, and before the humans come back they leave and return to their "normal" living grounds.