Thunder crystal
From Emps-World Wiki
The Thunder 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 thunder 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 Thunder crystal or the original weapon with a 50-50 chance.
