This spell is quested from Ancient Muramite Rune or Ancient Shadowspine Rune turn Quest... This is from Zones such as CoA and/or Dreadspire, The Demi-Plane of Blood
Both can drop off of some of the highest mobs in the harder zones. Yes you need to be in a High End Guild... To even see one of these Runes drop... And on my server they rot all the time.
Edited, Thu Apr 13 11:35:56 2006