Mount Osohai was a mountain, along with Mount Thunder, in the Dragon Spine Mountain Range on Angel Island. It was a massive peak surrounded by jagged rock spikes for foothills, and as such it had never been ascended. A Chaos Emerald fragment crashed into it after the original gem was split in two by Dr. Ivo Robotnik, and Knuckles the Echidna used his gliding abilities to reach the mountain and investigate. The Emerald fragment began burrowing through the rock to reach Angel Island's sole Chaos Emerald, and the mountain began shaking and dropped a rock that knocked Knuckles unconscious, though he was fortunately saved by the Ancient Walkers. (STT)
- Its name is most likely a pun on the term "oh so high".