Actualy it's from Warhammer. This is half of the chaos god Khorne's(one of the big four chaos gods to be exact) Battle cry and his only prayer. "Blood for the Blood God, Skulls for the Skull throne."
Warhammer 40k takes place in the grim dark future of 40,000 years in the future in which there is only war between the Imperium of Man and all other forces. All FTL Travel relies on entering a coterminous dimension of psycic energy and roiling storms of emotion and magic. The entities of this place are often malignant as foul emotions are more common and more powerful than good ones. One of the strongest of these beings is Khorne the horned Brass and Crimson trimmed deamon of violence and combat.
As Galactic Civilization has fallen into a dark age of violence and superstition he is obviously a very powerful being being fueled by the blood lust of many sentients(there are some notable exceptions!) The setting is basicly western fantasy in space with Orks, (Bioengeneared Angry Fungus of Warrrrhhhh!) Eldar (our decadent civilization of space elves was destroyed by the birth of Slannesh the God of Pleasure and Secrets), Knights/Space Marines (the Adeptus Astartes lives to serve the Immortal God-Emperor of Mankind), even Undead (skeletal soulbound robots of black living metal serve energy eating star gods who will harvest your souls.)
The setting manages to be very silly yet dark at the same time.
[ April 24, 2008: Message edited by: Belteshazzar ]