Stygius is a weapon that requires to be somewhat up close and personal if you are using the base model. When you are going into the fights, it is best to use dash strikes for most of your attacks rather than going in with combos unless you are using the Aspect of Arthur or Nemesis. Stygius combos well off of dash strikes and specials. Combo chain these two attacks and you will melt through most enemies. Once they begin obtaining armor, start implementing casts more often into your play style. Follow this and continue refining. Eventually you'll blast through all three biomes easily.