There was a post on the WoW Druid Forums asking this question. Someone posted the idea that the Wrath spell is simply us druids shooting cabbages at our foes.
I figured it was mainly some lines of code that were animated to look green and sparkly that caused damage to whomever I deemed worthy enough to throw it at.
Orrrrrrrrrrrrrrrrrrrrrr!
My take is it's Elune's way of channeling her "wrath" so to speak through a conduite to punish those who commit crimes against nature.