Jasper can be used to change an Eternal Wand to an Eternal Lance.
Myth Stone can be placed on an Eternal Item if it has an empty Socket.
Aethereal Drain Set taken off and replaced with Momentum Set.
Legend Multi Attack taken off and replaced with Crystal Gold Find.
Legend Glasscannon taken off and replaced with Epic WD%.
Epic ED+ taken off and replaced with Epic WD+.
Legend Push the Limit not changed.
if this was found after defeating a high level mob, then this would be a Bug and needs to be reported in the Bug Report Thread.
the only other option is that a Cheat or Hack was used to modify this item. all anyone has to do is to compare an Eternal item in the Codex to the list of Crystals I posted, to see if the Eternal Item has been legitimately Crafted or not.
I hope this clears up any confusion.