Interstitial beasts

Once purveyed at Stavanger's Den of Interstitial Beasts, rarely seen since the Kraken rose, but for some reason beginning to return. These are all creatures which coexist with spaces, slip through cracks, and so on. Named beasts include:
 * book-bugs/book-scorpions
 * joist-bearers
 * eve-hounds
 * footing-frogs
 * mirror-hags
 * cork-clingers