Fire crystal
The Fire crystal is dropped by Tormented demons with a chance of 1 in 500 kills. It upgrades the Abyssal whip, Donator whips, the Elemental bow or the Elemental staff to their fire elemental upgrade, consuming the crystal in the progress.
The upgrade is not reversable and turns the weapon into a more powerful but degrading state, turning into the Fire crystal or the original weapon with a 50-50 chance after 5000 attacks in combat.