The Giant Blacksmith gains the ability to ascend weapons down the Crystal path after receiving the Crystal Ember. Creation of a Crystal weapon requires a standard weapon +10, Titanite Chunks for upgrading to +4, and a Titanite Slab for upgrading to +5, as well as the requisite souls.
Crystal weapons are functionally very similar to weapons upgraded down the Standard path: they deal only physical damage, can be augmented, and in some cases increase scaling with Strength and Dexterity.
However, Crystal weapons have some important characteristics that set them apart from Standard weapons. Crystal weapons deal higher damage than Standard weapons, making them the most powerful choice for Dexterity and Strength builds. On the other hand, Crystal weapons cannot be repaired, and their durability is reduced to a tenth of its original value. For example, an item which has an original durability of 200 will have a durability of 20 as a Crystal item.
As a consequence of upgrading weapons and shields down the Crystal path, once the item's durability runs out, it can only be restored by upgrading. Once a +5 Crystal weapon breaks, it is permanently lost. Thus, the Crystal upgrade path is most suitable for weapons which can be re-obtained in the same play-through. Unlike other upgrade paths, Crystal weapons cannot be reverted to their standard state.
Further reinforcing Crystal weapons restores their durability.
Using the East Wood Grain Ring can extend the life of Crystal weapons by slowing the degradation of the weapon.