Jack Williamson 
One Against the Legion 

"I am omnipotent and omniscient. I want every man on every planet to shudder and grow pale when he thinks of Me. For I have suffered gross injuries that must be avenged…"This sinister message — and a loathsome serpent-like trademark — were the only clues the Legion of Space had to the identity of Mankind’s most evasive and horrible enemy. But meanwhile, He or IT — had meticulously begun to destroy the world…The Legion of Space was well accustomed to facing mortal peril in the black depths of outer space in order to defend humanity against its unearthly foes. But even they were to find their courage and ingenuity tested to the utmost limits in their fight against the vile phantom that called itself God and shrouded the Universe in an incredible web of terror…