Itch was a rather unusual bodily signal. Counterintuitively, it and the itch one felt when being tickled were actually two entirely different things.
The latter came from mechanoreceptors in the skin, its pathways tied to touch and movement. It triggered defensive responses, making people aware that something had crossed their safe distance and prompting them to evade and struggle.
The former, however, was governed by a specialized set of nerve fibers, activated by various inflammatory mediators. It ran parallel to pain sensation while remaining independent of it, and the two inhibited each other. That was why scratching could bring relief, while that temporary relief made the brain inclined to keep scratching, even tearing open the skin when the sensation became unbearable.
The former was within; the latter, without.
And "an itch that sank into the marrow" undoubtedly signaled a drastic change within the body. A reaction of unknown origin was rapidly unfolding, threatening to spread like wildfire in mere moments.
He rolled up his sleeve and saw a rash spreading in tandem with the itch. Centered on the fragments embedded in his skin, it was congested and swollen, forming broad red welts like severe hives.
Beneath the epidermis, the itch continued to diffuse deeper, gradually developing into a faint burning sensation. A dull ache, like copper beads rolling, traveled across his bones, while his joints stiffened as though cast in molten iron.
His arm was like a waterskin filled with boiling water, hot and taut, yet somehow always capable of holding more. There was no moment of rupture—only an ominous numbness spreading from the worst-afflicted areas, swallowing normal sensation.
A murky, impossible-to-conceal pallid glow appeared on the surfaces of the Embedded Bodies. They had lain dormant for so long, hiding beyond the immune system's surveillance, that even their host had