Crystals

Elemental Crystals can be obtained as a rare drop from Tormented demons. These four types of crystals can be used to upgrade Abyssal whips, staves, bows and their dyed variants, the Elemental bow and the Elemental staff into four primary nature elements, gaining the prefix (fire), (thunder), (ice) or (nature) behind their name:

Fire crystal
Thunder crystal
Ice crystal
Nature crystal

To upgrade a weapon with a crystal you simply use the crystal on the weapon in your inventory. Once upgraded with one of these crystals, the weapons become upgraded and degradable. After 40,000 hits the crystal is destroyed and only the original weapon remains.