For example, it's possible to fill a common soul gem with either an lesser or petty soul, while a greater or a grand soul can't be stored in common or soul gem of lesser quality. Like in Skyrim, white souls vary in strength from petty to grand, with five soul gems of different capacity in total and they can be acquired from creatures. Soul gems, or Pyrean crystals, are used trap the soul of any creature with a white soul.
