Kill everything you can kill before you jump into the second trench. The first batch of behemots you can handle by getting into the tunnel and hitting them from a distance. That makes it possible to find a spot where you can cast invisible. Then jump down, go in the opposite direction from the exit, usually it is possible to sneak past the 1-3 behemots that blocks the way, and either throw sparks at them from the narrow bridge that leads to the hidden door, or use that tunnel to hit them from a distance. Or get GM water first and LB back up and then hit them with sparks from that ledge.
Part of the fun is to find easy ways of doing difficult things.
