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Make sure to cleanse yourself using the buckets around the nearby forest before you fight.

Otherwise it's kind of just an endurance match. Make sure you're healthy as you can be when you start the fight. Try and pay attention to the enemy's attacks, as sometimes it becomes resilient to specific things and you might waste your resources.

Besides that just try and use all your skills, use your items, don't hold back. There's no specific strategy, it's just an endurance match really.