Professor Armitage began studying spellcraft from various Eldtrich tomes after the events of the Dunwich Horror. It helped him piece his mind back together. His broken mind found order within the chaos. He returned to his professorship at the Miskatonic. However questionable practices with students led to his firing.
In the mean streets and shadowed alleys of Arkham, he began seeing portents of a war between the creations of the Elder Gods. Thus he set out to acquire various pieces of Eldritch lore/tomes to add to his spell repetoire, crossing paths and arcane knowledge with the likes of the Haunter in the Dark, the Hound, the ghouls, the Deep Ones and the shoggoths.