Game:Clayton

Strategy
In the first stage of the battle, Clayton's only weapon is a shotgun, good for distance attacks, but he also fights alongside a bunch of Powerwilds. Ignore them and lock onto Clayton, bashing him until his HP is about halfway down, but be warned halfway through his life he will use potions. At this point, the second portion of the battle begins.

When up against Clayton for the second time, the cliff walls explode and Clayton mounts an invisible creature, the Stealth Sneak. His only weapon is still a shotgun, which is easily reflected and does not do much damage regardless, so Clayton himself actually poses no true threat, so focus on the Stealth Sneak. Dispose of this creature first, then find Clayton and bash away at him. Your prize for winning is the Cure spell.

Clayton may heal himself in the middle of a battle. But his only way to attack is his shotgun. All you need to do to deflect it is to hit it right back at him, or perhaps use Guard. Note that even in the battle with Stealth Sneak, once you defeat Clayton, the battle ends.