Complex sentence: The principal peaks of the Revelation Mountains are granite spires, rising out of relatively low-elevation glaciers, making for large vertical relief and challenging climbing despite the low absolute elevation of the peaks.
Split into simpler sentences: The principal peaks of the Revelation Mountains are granite spires, rising out of relatively low-elevation glacial valleys. The vertical relief in the Revelations makes the range a very dramatic place and creates challenging climbing conditions, despite the low absolute elevation of the peaks.