Complex sentence: After discovering the Pendragon is the late King Artorius, cursed by the Horned Crown Morganthe Tricked him into wearing (the crown isn't part of the prophecy), you give him a potion and the land is restored.
Split into simpler sentences: After discovering the Pendragon is the late King Artorius, cursed by the Horned Crown. You give him a potion and the land is restored.