[quote=Gokiburi7]
So, with regards to Celestial abilities, could a morally corrupt character still use Light and Harmony?
[/quote]

I'd wager not since they are tied into a force that is ruled by the aspects of virtue. Though I imagine characterizations are a lot more complex than "saturday-morning evil" and "lawful stupid", it's likely there could be a priest who follows the path of light who is zealous to the point of murder but still believes in helping people and such.

Though that's not to say harmony is GOOD, as the virtue of justice is as ruthless as the sin of wrath can be.