Hárr is the patron god of the Normans' mythology. Before Normans started a battle, they will shout his name praying for his protection. Should they have fallen in battle, it is said that their soul will be taken to Valhǫll by Hárr.
Theory[]
Since Hárr is one of the names of Odin, it is possible that he is the same god named after Odin mentioned in Ys IX: Monstrum Nox. However, not too many information is provided currently to decide whether this is true or not.