MechaTarrasque
Hero
Just spitballing:
The power comes from the Oath. So it's not about belief, really, it's about actions. Taking a look at the Tenets of the Crown, here's the Things You Can Do To Break It:
As a DM, I'd probably be a little flexy on the Courage angle (as written, just running away from a fight might be considered an infraction), less flexy on the others. But to echo the advice upthread, the specifics of the player's goal for the character probably matters more than anything else.
- Law: Willingly and voluntarily disregard or break the laws of your land.
- Loyalty: Oppose your monarch's actions or openly defy and flout their commands.
- Courage: An open and craven display of cowardice; advocating for fleeing your enemies
- Responsibility: Flout your mandated guard duty, fail to submit to punishment for an infraction
So you could totally be a law-abiding, loyal, courageous, and responsible kind of Evil. I mean, that's Darth Vader (up until the final moments, anyway). That's the Malfoys. That's half of the "BBEG's Sidekick" characters out there in fiction.![]()
That makes me think of looking at the other half of the "BBEG's Sidekicks", and the best way for a Crown Oath paladin to fall would be to pull a Starscream.