(this whole thing is deeply trenched in headcanons so just Go With It)

fancy diamond is only a step below the diamonds themself. they work as a secretary/organizer for the entire empire, sending out orders from the diamonds, managing the managers of kindergartens, etc. just makes sure everything is stream lined and productive.

they are an odd gem entity, treated more as a living super computer than a person. they dont really mind- all fancy diamond cares about is making sure those stupid agates do what they're told. they are an amazing multitasker, at the expense of having an absolutely blank personality. their voice is dull, but the only time you hear them speak is when theyre barking orders at you. their screens and computers are always up, as they never stop working.

they have no arms, and use a sort of limb enhancer-like technology  to interact with things. four arms are more productive than two. they can float (they never touch the ground) and have telekinesis. they cannot summon a weapon.

however, they are no combatant. fancy diamond does not fight at all. they must be surrounded by a constant battalion of quartz soldiers to ensure their safety. their body is very weak and feeble. they also have a personal squad of pearls to do menial labor for them, since theyre always busy.

they are very strange and tend to scare gems that have to go to their 'lair.' fancy lives in a chamber deep below homeworld, a sort of central hub for all the activities that go on.

(and the second pair of eyes are just facial markings)