Archvale

This boss can be found in the Crystal Atheneum.
I used the Third Eye Tome to defeat him at the moment.
He spawn magical energy balls (LOTS OF ENERGY BALLS), comes at you with a dash sword attack, throws the sword at you, spawns circles on the ground from where energy balls will come at you. As for previous bosses I kept my distance and kept hitting him with the range attack

Here is a video of how I defetead the boss if it helps.