shortly after Lunighttemare killed Luigi, he and nightmaric took control of him, but Luigi was still in there, just not the same.....
and his body couldn't handle all of this control, so lunighttemare and nightmaric made the new body for them all, but after a while, they felt like they needed something, Luigi suggested a pet in the form of the dark star, which the other two agreed was a good idea, and the dark star is like Lord Amethysts pet. but his body became unstable, and began melting (cause nightmaric.) so they added some Robo attachments.
that's about it, see ya'll on ze flip-side.