The Invisibility Ray, used by Warren
The Invisibility Ray was a device invented by the Trio. As the name implied, the Invisibility Ray was a gun that made anyone and everything that was hit by it invisible. The device used the diamond they stole from the Sunnydale museum.[1]
The Trio intended on using it to sneak into an all-women's spa, but it overloaded when they saw Buffy Summers coming out of the hair salon and the beam hit her, making her invisible. When Buffy was hit, the mass amounts of energy that blasted her began to slowly break down her molecular structure and would have eventually caused her body to disintegrate. The Trio themselves were also made invisible. They used their invisibility to sneak into the arcade, but, after Willow Rosenberg discovered what it would do, Buffy confronted and beat up the Trio before Willow made her and the Trio visible again.