After freeing Shami-Amourae and dealing with the chokesnake, the next thing that is supposed to happen is the tearing open of a dimensional rift that floods the area with waters from the River Styx. It mentions the location (20' radius centered on Shami-Amourae) but nowhere in the module does it mention how high the rift opens above ground level. It states that the Lemorian Bloodscouts mounted on Retreivers come through the rift and are under the effects of feather fall.
I can just make a DM decision (maybe 200 feet?), but it would be nice to know what height the writers intended for the rift.