Oooh I have Tien headcanon I want to talk about. I will just converse into the void and maybe someone will read it.
The third eye thing reminds me of of Hindu mythology. In Hindu mythology Krishna got cursed. The curse was on Krishna’s bloodline and it was that no one in his bloodline would live to see future generations or something like that and so all of Krishna’s family/clan killed each other. So I was thinking Tien’s clan got cursed (magic related) and the condition was on activating the eye for fighting purposes, maybe they were a clan of assassins and they got cursed for spilling blood, going against the will of their deity.
So if anyone used the inner eye power up something bad would happen. So Tien’s family became pacifists and sealed the eye on some Naruto shit. Tien is basically the last of his people, his clan is probably mostly dead. I’m going with Saiyan Scholar’s headcanon that another group hunted them into extinction because they feared the power of the third eye. Tien’s mother is killed but he survives, eventually found by Master Shen. The intense, borderline abusive training, is enough to cause the eye to open but he has no idea how to fully activate it until he finally starts tracing back his roots. Now he is tempted and wants to get stronger at the risk of the bad thing happening again.
Also headcanon that the three eyed people built the Lookout. But after the curse they probably lost the ability to use it.