fusion range in short is the required lv of the componet demons to make a new demon. It can be calculate with a simple fourmula.
Fusion Range = Demon A's level + Demon B's level
some demons, like legions(72-75) have a very small fusion range so if the components are a lv off the results change (Pisaca or Vetala) as such, ranges are important to keep in mind when going along an inheritance chain.
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