<p>Lol, it's part of the persona of being a king, being a member of a royal family to have loyal and strong bodyguards and besides, the Soul King isn't invincible, no one and nothing is. For example., the God Tree of Naruto was the god who was literally omnipotent than an alien came down and stole it's sacred fruit, became like a goddess herself and overthrew the god tree, freeing the world from war and becoming it's beloved goddess who herself became corrupt having absolute power and was overthrown waay before the start of the series. Yes, spoilers to those who are into it and haven't finished it and don't know all the lore but it's not a big deal as it doesn't spoil the entire plot but the point is, even someone suppose to be omnipotent is still vulnerable to defeat.
</p><p>But back to the possible plot, the difficulty of openly oppossing them doens't mean impossible because they will make a mistake, everyone always does no matter how talented or skilled a person may be, no matter how much experience they have and when they do, the Royal Guard is a major asset to say the least as the Royal Guard has massive spiritual power and hundreds, even thousands of years of experience so they can make up for their disadvantage decently well like the main and side characters always do. Also, I wasn't saying to attack the coven directly but to pull this off, you can't give them too much power like being able to warp existence or grind time to a halt, that would be too extreme.Â
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