Rhys-Ball was a hijacked Pleasure Sphere from the Space-Laser Tag mission. While fighting through Skywell-27, Rhys had the Vault Hunters use a Viper Drive to let him take control of what they thought was a Death Sphere.
Because Rhys-Ball is a Pleasure Sphere rather than a Death Sphere, it doesn't have any weapons. The Vault Hunters have to defend Rhys-Ball as Rhys remote controls it over to the door to hack it. They continue to clear the way for Rhys-Ball so it can hack into the laser.