After Syntax got one of the items that would create the bone mech, Lady Bone Demon revealed to the Spider Queen that they need five more powerful artifacts to create it.
Once the bone mech was created, Lady Bone Demon used the mech to attack MK. Although MK was able to destroy the mech in its spider form, Lady Bone Demon rebuild it into the Bone Scorpion after MK lost some of his powers.
After MK destroyed the mech's scorpion form by creating the Monkey Mech, Lady Bone Demon changed into her true form and transformed the bone mech into the Bone Demon.
Monkie Kid's little red mech is on his high-flying cloud board, and he’s getting right in the face of the blustering bone mech. The Monkie mech can’t match the bone mech for power, but speed and agility are on its side. “Doink” goes its staff, right in the skeleton’s cockpit cranium. Time to rattle some bones!
Forms
Bone Spider
The Bone Spider was the first form of the bone mech. After the bone mech was created, Lady Bone Demon used the mech in its Bone Spider form to attack MK, but was eventually destroyed when MK enlarged himself.
Bone Scorpion
The Bone Scorpion was the second form of the bone mech. After MK lost some of his powers, Lady Bone Demon rebuilt the bone mech into the Bone Scorpion to continue her battle with MK.
Bone Demon
The Bone Demon is the third and final form of the bone mech. After the Bone Scorpion was destroyed by MK, the Lady Bone Demon changed into her true form and rebuild the bone mech into the Bone Demon. Since then, the Bone Demon acted as a large tower for Lady Bone Demon until she used the mech again during the final battle.
The bone mech's three forms were inspired by Baigujing's disguises in chapter 27 of Journey to the West, where Baigujing took on a different form every time Monkey King seemingly killed her.[1]