With the Basilisk war droids under their control, the Mandalorian Crusaders struck at worlds across the galaxy, conquering Kuar and assaulting the shipyards of Foerost. Aligned with the Sith Lords Ulic Qel-Droma and Exar Kun during the Great Sith War, the Mandalorians rode their Basilisks into combat during an attack on the galactic capital of Coruscant, and again during the fighting at Ossus against the forces of the Galactic Republic. At Onderon, the Mandalorian Basilisk riders flew in opposition to the world's famed Beast Riders. Following the end of the Great Sith War, the Basilisk war droids went on to become a powerful component of the Mandalorian Neo-Crusader forces during the subsequent Mandalorian Wars: Basilisk droids participated in battles at Cathar, Vanquo, Essien, and Althir III.
Following the Mandalorians' defeat at Malachor V in the final battle of the Mandalorian Wars, the warriors were commanded by the Jedi Knight Revan to destroy their Basilisk mounts as part of the terms of their surrender. However, not all complied with Revan's demands, and numerous Basilisk droids continued to survive with Mandalorians who refused to give up their beast-like companions, including members of Clan Jendri and Clan Ordo. Even still, the war droids' numbers dwindled over time, and by the rise of the New Republic, most Baslisk droids could only be found in the museums of the galaxy. The Basilisk droid remained a symbol of strength in the Mandalorian culture, and the design of later Basilisk droids could be found emulated in the StarViper-class starship manufactured by MandalMotors; the Mandalorian company also named it's Bes'uliik-class starfighter after the ancient war droids.
A beast-like droid, the Basilisk war droid visually resembled a mechanical cross between a Zalorian rock-lion and a Karran beetle, standing on its six legs—two clawed, powerful front legs, and four smaller hind legs—at a height that varied from 2.98 meters upward to closer to five meters, depending upon the model. The Basilisk's droid brain gave it a rudimentary, animal-like self-awareness of a semi-sentient degree, and though they could operate independently, the war droids most often took the role of loyal mounts to direction-giving riders, and had to be powered up or shut down externally in a process that took seconds. Basilisk droids formed powerful empathetic relationships with their riders, and were known to howl as if in pain when their rider was killed.
The bodies of Basilisk droids were heavily armored and often colored in shades of green, though others were known to display hues of gray, or red with gold. Mandalorian riders, who controlled the beast-like droids from protective armored saddles atop the Basilisks, were known to garnish their mounts with an assortment of their personal weaponry strapped to the droid's body, including axes, swords, and flashpistols. The war droid's open combat models were, themselves, armed with a powerful array of artillery: pulse-wave cannons and auto-firing laser cannons, shatter-missile launchers, and concussion missile launchers with a four-missile payload could all be found on or under the armored plates of Basilisks. At the droid's nose resided the Basilisk's primary weapon, a cluster of shockwave generator rods that together could form a burst of plasma capable of ripping through the hulls of starships. Even the droid's heavy claws that adorned it's two front legs, used mostly as landing struts or for walking on the ground, could be used for brawling, crushing obstacles, or tearing open the body of an opponent. Basilisk droids often carried a pair of deployable space mines, and war droids of the combat type could tow volatile atomic compression bombs between them, catapulting the nuclear bomb into an enemy ship or space station. Mandalorian tinkering eventually spawned countless customized variants of the Basilisk, such as the two-seated bomber, which accommodated both a pilot and gunner, while the designated stealth configuration bore lighter armament and supplementary engines. Later models departed dramatically from the original droid's design, incorporating closed cockpits and larger S-foils, virtually eliminating the droid's animalistic appearance in favor of a form more similar to a starship.
Basilisk droids could operate effectively on the ground, in the air, or in the vacuum of space, and sensor clusters located at the fore and aft of the war droid allowed the Basilisk to detect threats from all directions. On the ground, Basilisk droids were typically slow and lumbering, but could move at faster speeds when required. In aerial combat, the Basilisk's rear armored wing plates—typically tucked against their bodies while at rest—would lift up to expose a set of high-boost engines that allowed the Basilisk droid to fly at speeds up to 550 kilometers per hour. However, while the war droid could reach great speeds, especially during bombing runs, it was slow to turn, weighted down by its heavy armor, and without the stabilizer fins at the tip of the droid's tail section, a Basilisk in flight was hard to control.
With a level of intelligence slightly above that of typical domesticated creatures, the animal-like Basilisk droids formed strong empathetic bonds with their Mandalorian owners. These bonds allowed the droids to react almost preternaturally to the commands of their riders, and act as extensions of their own bodies. They were loyal companions, and were capable of serving as mechanical beasts of burden, carrying heavy equipment or towing large sleds laden with cargo.
In spite of their mechanical beast-like appearance and animal-level intelligence, a Basilisk acted more often as a gunship than a droid. Capable of operating in the vacuum of space—their Mandalorian riders dressed in pressurized suits of vacuum-sealed Mandalorian armor—Basilisk war droids were carried aboard Mandalorian warships, held in place by magnetic locks until being launched from drop bays, where they could participate in fleet engagements alongside other Mandalorian craft, even using their claws to latch onto opposing vessels. Pairs of war droids were able to coordinate the deployment of towed bombs against enemy starships or space stations. Basilisk droids could also enter a planet's atmosphere, and it was not uncommon for Mandalorian riders to direct their mounts in a surging dive directly from orbit to the planet's surface, using the rapid rate of descent to confuse the targeting computers of opposing ground cannons.
Within the atmosphere, Basilisk droids were used to conduct high-speed bombing runs, or provide strafing air support for ground troops while hovering. On the ground, the typically lumbering war droids were capable of significant bursts of speedy movement, and could use their heavy claws to batter or slice the body of a hostile.