Even as humans can be, the Kel'Regar, too, can be touched by madness, and it can drive them to push to ends incomprehensible by the sane. The work of one such, Kararemi'ar'Salm'Torat, the Menangerie of Mad Creation, is a twisted, living structure, tormented by years of loneliness and incomprehensible need.
Foot Coral. It attatches to a foot like moss, almost gluing itself to an organism. It gets its food supply from the ground, and does not leech off the host in any way. It is not a malignant organism, and is entirely harmless. But it only grows on human feet, and even then, never on the left foot. An organism that it grows on can feel touch through the coral, but not pain. Removal of the coral is painless, but why would you want to?
Texturally, if fells like a dry, non slimy amoeba.