Balisarius was ruthless and brutal in his military campaigns.

Source: https://screenrant.com/rebel-moon-did-balisarius-assassinate-the-slain-king/

If Balisarius is responsible for the Slain King's death, and he made Kora their bodyguard, was Kora involved?

Source: https://screenrant.com/rebel-moon-kora-backstory-dark-princess-issa-assassination/

It's quite conspicuous how Balisarius positions Kora as the bodyguard to Princess Issa, the royal family is betrayed and assassinated, Balisarius rises to power, and Kora goes into hiding as one of the most wanted fugitives in the galaxy.

Source: https://screenrant.com/rebel-moon-frozen-ice-lake-astral-plane-balisarius-explained/

It's quite conspicuous how Balisarius positions Kora as the bodyguard to Princess Issa, the royal family is betrayed and assassinated, Balisarius rises to power, and Kora goes into hiding as one of the most wanted fugitives in the galaxy.

Source: https://screenrant.com/rebel-moon-frozen-ice-lake-astral-plane-balisarius-explained/

To defend her planet and repel the invaders, she embarks on a quest to recruit a squad of fearsome warriors who must unite if they wish to bring down the tyrannical regent Balisarius.

Source: https://www.cbr.com/zack-snyder-video-game-rebel-moon/