Magnum Opus is an extremist rebel group of gems, based on the Roblox game 'Gem Galaxies'. It is lead by a brutal platinum named Iridi, an overseeing kyanite named Verity, and a fossilized opal named Leech. It was once lead by the creator of the group, known simply as 'The Founder', but he has since vanished. Magnum Opus is a firm believer that if you aren't with them, you're against them.

The gems of this group carry metal symbols embedded in their forms, known as 'brandings'. These symbols are alchemical ones, granting the gems unforeseen powers or boosts to their pre-existing abilities.