The physical manifestation of the worries and fears of the people of the Cloister. Appearing in an almost non-corporeal form, the beast seemed to possess teeth as well as a powerful exoskeleton. It's size was proportional to the fears of the Cloister.
The sanctuary beast was the last element preventing the remnants of the Cloister from ascending to be with their forefathers. Thanks to John Sheppard's words of wisdom, the people confronted their fear and defeated it, allowing them to ascend.
Epiphany - Colonel Sheppard continues to fight the sanctuary beast and protect the Cloister in the process, all-the-while dismayed with the fact that they are not willing to help him.