A key moment in the Manifest season 4, part 1 finale implies that an Omega Sapphire is literally inside of Cal. Discovered during the passengers' efforts to find an alternative solution to stopping the Death Date, the Omega Sapphire has quickly evolved into an important part of the lore behind the series. Based on what characters like Olive and TJ have been able to find out, the Omega Sapphires are tied directly to the divine consciousness that made the plane disappear in 2013.
Filled with the energy of the divine consciousness, the Omega Sapphires are powerful artifacts whose histories can be traced back to ancient times. Thanks to both the Callings and their own research into the matter, the Flight 828 passengers were able to uncover one of the lost Omega Sapphires, only for it to wind up in the hands of Holly Taylor's Angelina. Ultimately, the Omega Sapphire was destroyed, but a piece of the broken relic survived and became embedded in Angelina's hand, which may allow her to continue weaponizing its divine capabilities.
Cal's Dragon Scar May Hide An Omega Sapphire
The passengers have permanently lost access to the Omega Sapphire they needed, but one detail indicates that a second one might be hiding in plain sight. In the moment before Cal pulled Angelina into a Calling and defeated her, the arm bearing the mysterious dragon scar began to glow blue. Not only did this signify Cal's secret powers beginning to activate, but it may also be a sign that an Omega Sapphire is somehow inside Cal's arm. After all, the colors do match up.
Exactly how the Omega Sapphire came to be there is unclear, but such a reveal would provide a working explanation for the scar. In addition to identifying him as the Dragon, the scar may be the mark that hides the place where the Omega Sapphire's power is located. Also, this would tie in perfectly with what the prophecy deciphered by Olive and TJ said about Cal. Apparently, being "touched by an Omega Sapphire." This could have been taken as a reference to Cal destroying the one wielded by Angelina in the following sequence, but it may be that the prophecy actually refers to an Omega Sapphire that was already within him.
A Second Omega Sapphire Would Explain Cal's New Powers
The existence of an Omega Sapphire (inside Cal) would make sense of the fact that he possesses powers that no other passenger in Manifest has. As demonstrated by the finale, Cal can create his own Callings and pull other passengers into them. Since Angelina could manifest fake Callings with her Omega Sapphire, it does seem plausible that this is really what makes Cal so special in the series. Plus, it justifies Cal being strong enough to combat Angelina from his deathbed. The only answer to an Omega Sapphire's power may be another Omega Sapphire.