Well, the movie '13th Warrior' is indeed based on a true story. It takes inspiration from certain historical events and tales. However, like many movies 'based on true stories', it has likely made some adjustments. For example, the characters might be more dramatized, and some events may be reordered or combined to create a more engaging cinematic experience. But overall, the core of the story has its roots in historical facts.
It's not a true story. Warrior (2011) was written and directed to tell a compelling fictional narrative that engages the audience without being rooted in reality.