What If Jax was a Cosmic Being
What if Jax was cast out from the star like Soraka did. Jax tried to stop what ever was happening in Icathia which resulting in him being cast out.
Soraka and Bard are not allow to intervene with the affair of mortal but Soraka still did, who to say there wasn't someone before her who did so as well.
Even after losing her connection with the star Soraka still retain some of her power the same could be said about Jax if he descended as well.
Both Jax and Soraka have Purple skin and we know that Soraka skin use to be white/light if you look at her divine skin that change in color could be because they lost connection with the stars.
Jax also have symbol on his clothing that are similar to the symbol that Bard uses.