I'm running a Starfinder game, and one of my players is playing a Mystic Overlord. They're the party face, and use the Charm Person spell to mak everyone like the party. I don't want to make this impossible, because it's what they've built their character around and has lead to some cool non-violent solutions, but I'd like to have things in place so it won't always work. Are there any abilities or items that would negate Charm Person, or should I just make sure important NPCs have strong Will saves?