- "Some say the coral implants ruin our slaves. Only the weak ones."
- ―Yuuzhan Vong slaver
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. 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.
- Boba Fett: A Practical Man
- Invasion: Rescues 3
- The New Jedi Order: Dark Tide I: Onslaught (First appearance)
- The New Jedi Order: Dark Tide II: Ruin
- The New Jedi Order: Agents of Chaos II: Jedi Eclipse
- The New Jedi Order: Balance Point (Mentioned only)
- The New Jedi Order: Edge of Victory I: Conquest
- Emissary of the Void (Mentioned only)
- The New Jedi Order: Star by Star (Mentioned only)
- The New Jedi Order: Dark Journey (Indirect mention only)
- The Apprentice"—Star Wars Gamer 8 "
- The New Jedi Order: Enemy Lines I: Rebel Dream
- The New Jedi Order: Traitor
- The New Jedi Order: Destiny's Way
- The New Jedi Order: The Unifying Force
- Legacy 15: Claws of the Dragon, Part 2
- Legacy 27: Into the Core (Mentioned only)
- Legacy 29: Vector, Part 10 (Indirect mention only)
- Legacy 30: Vector, Part 11 (Mentioned only)
- The New Jedi Order Sourcebook
- Ultimate Adversaries
- The New Essential Guide to Weapons and Technology
- The Complete Star Wars Encyclopedia (See coral restraining implant)