Notice how most of the Yuuzhan Vong warriors have “spikes” or “horns” on their back from their armor? Their armor, called “Crab Armor” or “Vonduun Skerr Kyrric” is resistant to lightsaber strikes and plasma projectiles. But the “spikes”?
The “Escalation Ceremony” is a religious ritual by the Warrior Caste that attachment of Implanters on their backs along their spine that officers receive as they rise through rank.
The implanters were small, gray and six-legged. They were equipped with botyroidal optical organize and a quartet of appendages efficient for slicing through flesh and tucking surge-coral into open wounds. The implanter carried whatever enhancements were necessary for the ritual escalation.
Most starting Warriors, eventually get two finger-length horns of coral on their backs that were two pointed tips, which are hooked slightly.
The implanters secure themselves to the back of the candidates’ neck to reach both shoulders. Sharp appendages make deep cuts on the tops of the shoulder muscles, clear down to the bones that form part of the ball-and-socket joints. When the incisions were complete and Priest Caste acolytes had collected the flowing blood in bowls, the implanters inserted the hooked horns into the cut, employing a resinous exudate they produced to weld the horns to the shoulder bones and to seal the wounds around them. At the same time, a sluglike ndgin wove a helix trail through the candidates’ feet, sopping up whatever blood the acolytes failed to capture.
Though perspiration ran freely and legs trembled, not one of the junior officers cried out in pain or so much as grimaced.
The candidates did not squeal because that would be seen as weak and unworthy of Escalation. If they squealed they would be demoted to the shamed caste, the lowest caste. All these activities took place after a prayer, then an invocation by the commanding officer.
(Star Wars – Agents of Chaos II: Jedi Eclipse pp 170-171 by James Luceno)