Sham's The Enemy Within
The Demon’s Tooth was a curved tooth about 9cm long, looking like a fang from a particularly ferocious predator. It seemed inert, but anyone who could sense the power of Chaos and who came within a meter or two of it could detect it and realize it was powerful.
As the only remaining solid part of the demon Zahnarzt, it had strange abilities. Firstly, with the proper incantation, it would begin to move very slowly in the direction of the Moon’s Egg: it was used in the creation of the Egg’s powers and still had an affinity to it. By charting the direction of its movement, the party could work out the direction to the Egg. The same incantation stopped the Tooth’s movement. It had other abilities that were never entirely revealed to the party. It was destroyed/absorbed by Moon’s Egg during the ritual to sacrifice her with it at the Unseen Library.