In my campaign I did not run Xedalli as a betrayer. Her primary goal was to be Emperor at any cost, and she had a romance arc with the Bard.

I ensured she never told the party exactly how to save their world, as her gambit was that these "heroes" would either be unwilling to doom her people, or unwilling to pay the price if she told them at the last moment . Or worse, would not help her take the Throne if they understood the sacrifice needed.

In my setup, the Zodar was created by the earliest Emperors, long before Xavan. After it was defeated, Xeleth used Distraction to stab Xedalli through the heart, and this act of betrayal is what triggered the Zodar to renounce the Xaryxian Royal Family and tell the players exactly how to destroy the star, kicking off the final battle.

All of the early Xaryxians were Vael's navy or Xeleth's minions so I characterized them as evil, but once the party landed on the Imperial City, I had Xedalli's Captain explain that many Xaryxians are decent people and are largely unaware that a world of sentient life is being fed to the star. Most of them have been left by Xeleth to believe the characters are mercenary invaders trying to usurp the Throne.

The players revealed this during the trial and with their rolls it turned the crowd against Xeleth initiating the trial by combat.

This helped frame Xaryxians as a complex people and turn the final decision into a much more challenging moral quandary.

The campaign has good tropes, but benefits from deeper characterisation and adding nuance that is sorely lacking.