Gram

Gram is one of the enchanted swords created by Devil Prince Regaccio, the blacksmith of the Devil Realm capable of creating powerful swords that become legend and mysteries in the world of humans. This sword was gifted to Dark Rance by the Devil Prince, who was fond of the boy and claimed that has "good eyes". It has the incredible ability to grow in size and power based on the anger and sadness of its wielder. The full extents of its power remain unknown but it's presumed to be really powerful when taken to the limit.