I might be late to the conversation and I don't mean to jump in too suddenly, but if you're still looking for an "evil" moon spirit, there's a common trope in the creation myths that were created in modern-day Philippines. I'm not really a master on the topic. I know more about how the geography of the Philippines influenced its mythologies than I do the mythologies themselves, but the trope goes:
The personification of the Moon is a greedy and jealous person who envies the Sun. The Moon does a crime which offends the Sun or a greater deity, is defeated despite being the one to start the conflict, and loses some of their power. Sometimes, the lost power turns into the stars in the night sky or falls down to create islands. The Moon is much dimmer than the Sun because of the lost power.
All of this is certainly a gross oversimplification, but the story isn't consistent throughout the area so there'd be a lot to cover. I can share more, I just don't want my first post in the thread to be too long. Is this the kind of moon spirit you were looking for?