I did a solo scramble up to Dungeon Peak, starting from the Rocky Run "backdoor" trailhead. From Lake Lillian, I went left, around to a point about due west of the center of the lake. Then up, along an ill-defined ridge. It looks like a ridge on the map, but really it is a wide slope with a mix of open scrubby bushes and rocky areas to ascend or go around. I had to keep going further to the right (north) to avoid the cliffs along the south edge of the ridge. Near the top, I went too far right and ended up at a minor peak, from which I could see the true peak with dramatic cliffs. I went back down and around to the south a bit and easily found a way up to Dungeon Peak. Coming down was easier. It is possible to run into cliffs that are too steep, but there is always another way nearby.
2100 ft gain, 3 miles, 6 hours.