"No death is natural," proclaims the police lieutenant at the heart of William Peter Blatty's "Legion." But in this follow-up to the writer's cultural game-changer, "The Exorcist," some deaths are just off-the-charts creepy. Crucifixion, decapitation and exsanguination all come into the picture, and WildClaw Theatre Company doesn't flinch from putting it all front and center.