6. Blue Light

Wading through the flooded cave, Severian enters a large chamber.  He calls out for Thecla and his voice reverberates in the great cavern.  In the distance, Severian sees a glowing mist.  It grows and advances towards Severian, illuminating a series of man-made structures.

The light resolves into a series of humanoids with ape-like features, fangs, and luminescent fur.  The creatures encircle and attack Severian, who wields Terminus Est in his defense.  

Noticing that the man-apes appear wary of water, Severian backs into a stream flowing through the cave.  Undeterred, the creatures continue their assault.  Severian cuts down one after the next before being overwhelmed and dropping his weapon.