Krull (1983)

In the face of total annihilation by the omnipotent Beast's unstoppable hordes of Slayers, the young aristocrats of two hostile neighbouring nations--the brave Prince Colwyn and the fair Princess Lyssa--are about to come into union, and form an alliance against the common enemy. However, the otherworldly adversary is all-powerful, and before long, a fateful abduction will trigger a desperate quest to the evil entity's grim Black Fortress, as Colwyn and a handful of mismatched defenders are willing to dice with death to ensure the land's future. In this suicide mission, the magical, five-edged weapon known as the Glaive is their only chance of survival. Can Prince Colwyn slay the Beast, save Lyssa and Krull, the small planet in the middle of the vast galaxy?