Food for thought: Croakamancy is a discipline which presumably has its own section in the MK. In order for Croakamancy to work, a caster needs: 1. Corpses, 2. A Clear Mind.
If there's no violence to produce corpses in the MK, they must come from somewhere else. We know from one of Parson's Klogs that corpses de-pop if they're not reanimated or moved (assuming it wasn't a typo about moving them, and "moving" means they have to cross a hex border, then Misty's corpse could've been preserved if they'd tossed it on a wagon or something and taken it outside of the city).
Maybe unsavory sides sell corpses to Croakamancers who're looking to practice their discipline. Thoughts?
Also, on the arrows/"myth" topic: Probably was Jack demonstrating for Wanda the impending danger, since she had just woken up and was not exactly alert. Jack can do sound and images as illusions; presumably the "myth" bit is a combination sound effect/expository artwork intended to give you the impression that the arrow whizzed by/through Wanda but wasn't real.
I don't always Think, but when I do - I Think because I can.