Welcome to my ongoing let play of Amnesia: Rebirth, playing in ultra-wide (21:9)
After the unplanned tank mining experience, I find myself a number a floors down below the fort in a cistern. I encounter the glowing orb thing again and it shows me to a path at the bottom of the cistern. I just have to figure out how to get down there.
This episode covers the most of ‘The Cistern’ level