Yorik-Kul

Yorik-Kul, or surge-coral in Galactic Basic Standard, was an organic device used by the Yuuzhan Vong. Surge-coral was implanted into slaves, which would then allow the slave to receive mental commands from a yammosk or a dhuryam. This, however, came at a cost, since the wearers would eventually lose their sentience and become mindless beings. Slaves that had lost their minds were used as cannon fodder to absorb blaster fire on the battlefield. Surge-coral also caused its wearers to grow thin and vanish in the Force. Eventually, the Shapers developed surge-coral that was less detrimental to the slaves, which only caused pain instead of turning them into drones.

Jacen Solo was implanted with surge-coral after he was captured by the Yuuzhan Vong, which eventually allowed him to sense the Yuuzhan Vong through the Force. A'Sharad Hett was also the victim of said implantation during his own time as a captive of the Yuuzhan Vong. Over a hundred years later, Hett, as Darth Krayt, was plagued and slowly being killed by the surge-coral's effects. Krayt was thus motivated to find and use Cade Skywalker to heal him of his implants.

By 127 ABY, Sith Lady Darth Maladi and Zenoc Quah of the One Sith had created a strain of Yorik-Kul that, after implanted, would grow when exposed to Force lightning, causing extreme pain and even death.