One Dragon Ball Hero's God-Tier Powers Are Still a Complete Mystery

screenrant.com:

While the Dragon Ball series these days tends to focus almost solely on the Saiyan protagonists, this wasn’t always the case. Although Tien Shinhan already began to show signs of fading into obscurity by the Saiyan Saga, prior to this there was a decent amount of screentime and panel space being allocated to the mysterious martial artist. Despite his once prominent role, one side of Tien that was never fully fleshed out in the manga was his backstory and origin as a human with three eyes, but one interview with Akira Toriyama helps shed some light on his potentially godlike origins.

In his introductory arc, the 22nd Tenkaichi Budokai, the oddly three-eyed Tien Shinhan and his companion Chiaotzu were introduced as antagonists from the Crane School. It is then revealed that the Crane School is run and taught by one of Master Roshi’s oldest peers, known as Tsuru Sennin or Master Shen. Shen, however, has developed a philosophy directly in opposition to that of Roshi's, wherein martial arts is merely a tool used to impose one’s strength. Shen also believes that the most potent use of this strength is for assassination, promptly training both Tien and Chiaotzu as assassins. This, however, was really the most Tien and Chiaotzu’s backstories were ever fleshed out and the exact reason for why Tien had three eyes remained a mystery.

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In an interview with Akira Toriyama for a Dragon Ball guidebook known as the Daizenshuu 4, Toiryama touched on a question asked by a fan who wondered about Tien’s third eye. In his response, Toriyama talked about how in Asia, beings with a third eye on their forehead are thought of as godly and possess the power of “True-Seeing.”