Secret Worlds: Thermal VastDiscovered by
Your target is a pipe support just above a morph ball tunnel entrance - see the video for exact positioning. Perform a DBJ to reach it, and unmorph quickly to climb onto the object. From here, simply walk along the piping until you go through the wall. This secret world can kill you slowly, if you stay on the lava floor, or quickly, if you step off the lava and fall to your death (or if you fall too far to the left on entering the SW).