Spirit Tonic (Bound) is an item which can be used to restore 100 Spirit Power during the Underworld event.
Unlike the unbound version, these variant can not be traded or gifted to other players, and there is no way to unbound it.
Spirit Tonic (Bound) can be obtained as a Chain rewards during the Underworld event.
It is also sometimes added to the Token Box when an Battle Royale event precedes the Underworld event.
After the end of the Underworld event one Spirit Tonic (Bound) will be converted to one Power Potion (Bound).