Elements' Fury

Elements' Fury is dropped by Strunk, a crusader mage in Underground River.

In-game description
"The mage who crafted this strange dagger was obsessed with the four elemental planes and sought to create a means to join them together. Opening portals to all of them at once, he managed to join their energies together to enchant this relic, giving it properties of each plane. Unfortunately, he happened to be standing between the portals, holding the dagger in his hand; when the energies converged, they converged on him. It was the mage’s apprentice who discovered the dagger, clutched in his master’s charred and frozen hands."