Solitarium is a type of magic rock that was only relevant in the Robot Masters storyline so it could do magic things and then be forgotten.
Robot Masters online mini-comics
Starscream created four melee weapons from pure solitarium, which he then fashioned into the Arsenal Force.
Most toys in the Robot Masters line came with a new accessory. Six of these were explicitly forged from solitarium...
- RM-04 Wrecker Hook's "Boost Hammer"
- RM-06 Air Hunter's "Sacred-Cut Sword 'Armorkiller'"
- RM-08 Wing Stun's "Jamming Trident"
- RM-09 Psycho-Orb's "Calamity Defenser"
- RM-13 Smokesniper's "Radial Pod"
- RM-14 Gigant Bomb's "Pulverizer"
The Hammer, Sword, Trident and Defenser could be combined to form the Arsenal Force megaweapon. Though it is not explicitly shown, the Pod and Pulverizer can also be added to the mix.
100 sets of special clear-red versions of these four weapons were made available as a contest prize (along with red versions of the three Autobot guns), as second place in the same contest where Cybertron City was first prize.
Each of the mail-away "Limited Black Version" Robot Masters toys came with a chrome-gold version of one of the four Arsenal Force weapons.
- RM-01 Optimus Prime - Gold Calamity Defenser
- RM-02 Megatron - Gold Sacred-Cut Sword "Armorkiller"
- RM-11 Optimus Primal - Gold Boost Hammer
- RM-12 Starscream - Gold Jamming Trident
There are other new accessories in Robot Masters that are not explicitly solitarium weapons. The nameless missile launcher included with Optimus Prime, Megatron, and Optimus Primal (and their redecoes) could be considered a solitarium weapon.
Also of note is that the extra chromed weapons from the first Robot Masters Autobots are the same transparent plastic as the solitarium weapons underneath the chrome coat. These were included in the contest-prize weapon set in clear-red without the chrome coating, so perhaps those versions are forged from solitarium.
- It has been speculated that the new-mold weapons in Robot Masters are actually unused accessories from the Takara "LED Powers" Microman series, which was abruptly cancelled in late 2000. The last section of the line included transparent plastic weapons that could be combined to form armor or larger weapons for the individual Microman figures. The handle size is also identical between the solitarium parts and the "Shining Tector" Microman weapons.