since no class is inherently designated for good/bad people, what do you imagine an evil Muse/good Lord would be like? I always pictured evil Muses as being more Machiavellian in how they set the stage / conduct the symphony, but I can't quite place my finger on things

Good Lords may be actually just rulers, taking control of the situation and pulling at the strings, commanding for their benefit, but with said benefit being shared by others as well? Imagine playing Black & White, the God Game, and you’re kind of doing all you can to prevent your cities from being taken and shutting down the enemy. Sure, you’re helping your cities, but you’re also getting worship energy from them, so protecting them is to your own benefit. Basically just. If a Lord isn’t an asshole looking down on those beneath them.

Muses are an interesting Class to make bad, because they’re classically associated with Martyrhood and very passive intervention. But it’s because of that that they could make some amazing villains. ‘For the greater good’, even when the Greater Good is completely impersonal and horrible for everyone else. I don’t quite know enough about WoW lore to peg him as a Muse, and even then I don’t quite think he is, but Sargeras is trying to corrupt with Fel and destroy all the World Souls so the Lovecraftian Horrors beyond the Universe can’t get to them- He’s, in essence, corrupting and destroying the Universe, but his motivations fall under the passive spectrum rather than the active. Likewise, evil Muses would have goals, objectives, that while sensical and just to them are reduced to fucking everything up, forever. “I can’t see you suffer” kind of types that kill without a moment of hesitation.