First Referenced:
The Crushing Fist (Part 6)
Other References:
The Crushing Fist (Part 7), Our Final Acts (Multiple parts)
The Purple bio-stone is a crystalline technology, used to allow long distance and inter-dimensional telepathic communication between two people with the stones implanted in them. In addition to the telepathic communication, the stones also allow a level of connection and control over another individual, as in the case of Cristina Thompson and Ward Shaw (The Sword). Likely the method and location of implantation influences the level of connectivity and control influenced by the bio-stones.
The Purple bio-stones are known to interfere with devices that interact with the soul, such as the Soul Reader (Book), which malfunctioned and released dangerous spectral energy when used against Ward Shaw (The Sword). The interference isn't restricted to technological constructs, as the stone embedded in the spine of Ward Shaw (The Sword) was able to knock the trapped soldiers that were to become The Black-eyed Army loose from their captivity and torture at the whims of the Shadow Entities when they attempted to slice his soul away from his body.