The Morrígan
Several models were combined for this project.  The base figure is Archaon from Warhammer (Games Workshop).  Archaon's head was replaced with a Warhammer 40K (Games Workshop) Sisters of Battle Cannoness head.  The spear is a combination of three spears from the Warhammer Skeleton sprue.  Other modifications include the removal of the spikes and Chaos brand from the horse, removal of Archaon's sword and shiled mount, and the breastplate modified to match Sisters of Battle armor.