А зачем тебе это, с какой целью? assassin вро де бы переводится просто, как "убийца". Думаю Говард в этом смысле и употреблял данное слово, а не имел ввиду какую-то организацию. и переводить его на русский следует именно. как "убийца", а не "ассасин".

"Publius feared a plot to trap and slay you beyond the frontier," replied Prospero, smoothing his silken surcoat over his shining mail, and admiring his tall lithe figure in a silver mirror. "That's why he urged you to remain in the city. These doubts are born of your barbarian instincts. Let the people snarl! The mercenaries are ours, and the Black Dragons, and every rogue in Poitain swears by you. Your only danger is assassination, and that's impossible, with men of the imperial troops guarding you day and night. What are you working at there?"

For a brief space the assassins crowded him fiercely, raining blows blindly and hampered by their own numbers; then they gave back suddenly — two corpses on the floor gave mute evidence of the king's fury, though Conan himself was bleeding from wounds on arm, neck and legs.

She imagined their fall echoing thunderously through the cavernous city, rousing ragged rat-eyed figures in hidden lairs among the sewers. Every shadow seemed to hide a lurking assassin, every blank doorway to mask the slinking hounds of darkness.

Murilo believed the Cimmerian would keep faith with him. Whether the man would be able to carry out his purpose remained to be seen. Men had attempted to assassinate the Red Priest before, and they had died in hideous and nameless ways. But they had been products of the cities of men, lacking the wolfish instincts of the barbarian. The instant that Murilo, turning the gold cask with its severed ear in his hands, had learned through his secret channels that the Cimmerian had been captured, he had seen a solution of his problem.