The 'hero / heroine' was a woman who changed into a man because in medieval times man are more powerful. He uses his tech from the future to help him protect his king and has a sword of modern alloy. He is stronger, faster, cleverer than his peers and saves some children in a bay from water monsters by a huge harpoon throw and diving in and killing the monsters. That's about all I've got other than most of the names were really weird and unpronounceable. If you get it you win a prize