Crystallized souls

Crystallized souls are items made in Soul crystalizers. They are made by connecting a crystalizer to a circuit with enough souls to create one crystal. If you add even more souls with a crystal already in the crystalizer then, it upgrades the soul crystal a higher level. They can be used on Soul Harvesters to create souls for an infinite amount of time, but low-level crystals output souls slower than high-level crystals.

There are 7 levels of crystallized souls. This method of farming pays off best by using high-level crystals, so it is advised that you to have already stocked some souls before you begin. Also note, it is better to level up a single crystal at a time instead of upgrading multiple ones.