I like, I really really like.
Particularly that "in whispery, crackly voices like an old radio." bit, that's fucking gold, radios do make all sorts of creepy noises, adding to the creepy factor is the knowledge that you're listening to signals that surround and permeate you every bit as much as regular sound does, except you can't hear it without a radio!
Have one with a cape (maybe just leather, chain mail is bloody heavy) smaller than the others, faster, smarter, so even if the protagonists escape the big ones they're still at risk, think of this one as an enabler for the others, not strong enough to attack directly but cunning enough to set traps, lock doors and play mind games, there's no paranoia quite like having a clever person out to get you.