Moon Powers are abilities that can be unlocked when a brawler has obtained a Star Power. Unlike Gadgets, they give some unique buffs for the Star Power to make them more powerful. Note that the original Star Powers can still be used, but are less useful.
Here are some examples:
Creepy Harvest: Life Drain. When Mortis hits an enemy brawler, he instantly heals 400 health.
Coiled Snake: Long Dig. Mortis gains even more range when his Coiled Snake bar is loaded.
Smoke Trails: Dimension Master. When Leon goes invisible, he is Immortal and also cannot be seen from close range. The only way to stop Leon from making invisible is when he attacks, or when the countdown for The invisibility ends.
Invisiheal: Force Fuel. When Leon goes invisible he instantly heals up to full health instead of healing for a few seconds.