Factual error: Ghost's sword has runic writing on it which is all well and good except it's written in English. It says "Thunder Sword".

Continuity: The writing on Ghost's sword early in the film has the Turisas rune (representing TH in Thunder) near the hilt, but later not only is a different font used but now the Dagalas rune (representing the D in sword) is at the hilt.