Crocoburio's Strength

 is a ring.

Description
''This ring has been blessed by the Dark Breath of Grougalorasalar, giving it great powers, now a bit weakened. This relic was intended for Crocoburio, the only one capable of mastering it without being dominated.''

Note
(Don't know how you get this. Only seen in a shop. Statistics shown here based on only 2 examples)