Amphistaffs represented a form of genetically-engineered serpentine life. They functioned as the primary anti-personnel weaponry utilized by the Yuuzhan Vong.
Consistent with the Yuuzhan Vong's reliance on biotechnology, amphistaffs were completely organic entities. They originated on the Yuuzhan Vong homeworld. Young amphistaffs developed in groups of three from tough, leathery polyps. They would extend outwards, seizing any available prey and directing it into the polyp's open maw, known as the groundmouth, which simultaneously nourished all four organisms. Eventually, the amphistaffs grew to lengths of approximately 2 to 3 meters, becoming too large for the polyp to sustain them. They would then detach, escaping their amphistaff breeding gla, and move into the wilderness, leaving the polyp to perish. Amphistaffs possessed the ability to perceive infrared light.
Mature amphistaffs were resilient and intelligent predators. Within the serpent's body, power glands could generate electrical impulses that altered the creature's semicrystalline cell structure. This field projected a millimeter from the amphistaff's surface, creating extremely sharp edges capable of cutting through prey. Only vonduun crabs matched the amphistaff's structural integrity. After consuming substantial amounts of food, amphistaffs would transform into polyps to perpetuate their species' reproductive cycle.
When a warrior captured an amphistaff as it separated from its polyp, a bond formed between them, and the amphistaff would faithfully serve its new master in combat. The warrior could use hand gestures to prompt the amphistaff to either harden or become flexible, depending on the situation. Amphistaffs could assume three distinct forms: a quarterstaff, a spear, or a whip. When hardened into a spear with a venomous tip, the amphistaff could be thrown, further enhancing its deadly potential. As a flexible whip, the amphistaff could ensnare or restrain its target, and also deliver poison. Amphistaffs were among the most durable materials known, impervious even to lightsabers. When employed as a heavy staff, the serpent could withstand repeated blows from Jedi weaponry without being affected. The amphistaff's edge, measured in atoms, could effortlessly slice through flesh. In an instant, the amphistaff could soften and wrap around a lightsaber's blade, its venomous jaws attacking the victim's face. Due to their organic composition, these creatures could recover from almost any injury. Virtually indestructible, an amphistaff could only be killed by repeated blunt force trauma to the head or decapitation.
Psychological trauma was common among Republic soldiers who engaged in ranged combat with Yuuzhan Vong armed with amphistaffs. When commanded, an amphistaff could project venom up to 20 meters. This spray was directed at the target's eyes, causing immediate blindness. The poison would then penetrate the skin and enter the bloodstream, disrupting circulation and restricting oxygen flow. The victim would experience excruciating pain for twenty hours before succumbing to death. Jedi Master Mara Jade Skywalker eventually developed a biotoxin drill that, if administered promptly, could neutralize the venom's effects.
Certain specialized types of amphistaffs, or related organisms, existed within the Yuuzhan Vong society. Supreme Overlords like Shimrra Jamaane wielded uniquely large versions of the typical amphistaff, known as Scepters of Power. Warmasters such as Tsavong Lah and Nas Choka were granted "Batons of Rank" referred to as tsaisi. Additionally, there was the Scepter of Entreaty, used when seeking an audience with the Supreme Overlord. There also existed a species of amphistaff that could be implanted within the body which could be used by infiltrators as the amphistaff would avoid detection until the appropriate time at which point they could be used. Finally, the reptilian Chazrach slaves were equipped with coufees, dagger-like creatures that were smaller, less flexible, and inferior versions of the amphistaffs, designed to compensate for their small size and limited combat abilities.
In 33 BBY, Darth Maul engaged in combat with a Yuuzhan Vong warrior wielding an amphistaff during his time in Cog Hive Seven.
During the Yuuzhan Vong War, the wider galaxy first encountered amphistaffs when the Praetorite Vong infiltrated ExGal-4 on Belkadan. The advance agent Yomin Carr, a member of the Yuuzhan Vong empire, used this weapon against Jedi Mara Jade Skywalker.
A number of hibernating amphistaff's were smuggled onto Hosk Station in order to arm elements within the Givin government who were sympathetic to the Yuuzhan Vong. The aim was to create an uprising when the Yuuzhan Vong fleet arrived in the system thus securing the location.
Jacen Solo, while aboard a Yuuzhan Vong seedship, utilized his Vongsense and connection to animals to gather seventeen young amphistaffs to his side and help him against the Yuuzhan Vong crew onboard the ship. He used these feral amphistaffs to also slay several of the larval Dhuryam in order to sabotage the shaping of the planet Coruscant.
Near the end of the war, a group of warriors crashed on Zonama Sekot, the Yuuzhan Vong's original world. As the warriors disembarked from their downed coralskippers, their amphistaffs detached and fled into the tampasi. All remaining amphistaffs were loaded onto the Yuuzhan Vong warships and sent crashing into Coruscant's star.
In 137 ABY, Jariah Syn journeyed to Wayland, where he successfully tamed a native amphistaff and employed it as a weapon, naming it Heartstriker.
The concept of the amphistaff may have originated as early as the Bantam/Dark Horse invasion storyline, where the (non-humanoid) invaders were intended to be armed with a bladed weapon capable of resisting lightsabers.