If you're looking for opportunities to strike at Watcher Knight, there are a few ways to make the fight easier. First, make sure you have upgraded your Nail to maximize your damage output. Second, explore the area around the entrance of Watcher's Spire to find any useful items or abilities that can give you an edge in the fight. With the right tools and tactics, you'll be able to defeat this fast and powerful boss with a large amount of health.