This is very well thought out, and the idea of hiding some secret malvolent scripture and spells in plain sight has great plot potential. Parasites have that unnerving factor to them, this is a great addition to a horror game. I can't think of anything that could make this better.
Tumble: this button appears to be a flower formed from several pea-sized beads. When removed from an object of clothing the beads which form the petals fall off, creating a slightly treacherous five-foot square for those who do not tread carefully. Concentrating on the button will recall all of the beads, but only within thirty feet.
I love it. I don't know why there is any discussion of whether it is a dungeon or not, it doesn't really matter as far as I am concerned. All a dungeon consists of is a series of encounters based on a premise in a semi-enclosed area. Check check check. The scenes are fabulous, the creature is awesome and this is definately a fantastic game-ender with some unique aspects.