Steps:
1. Just wait for him to jump on you, step forward and charge - parry afterwards (Holy Moonlight Sword untransformed is the best weapon for this part).

2. When he is close to half of his health, lure him close to the rocks and wait for the jump attack, charge and parry - throw him into the rocks (they are not accessible normally). Boss will be stuck on the rocks and stop moving - now take your revenge :)

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