From AQWorlds Wiki
|Use:||Get all three to unlock First Lord Of Chaos.|
|Location:||Otto (Area) in Mobius, Faerie, and Cornelis|
|Price:||Get it from doing all the quests and talking to Anna and Otto in Mobius, from doing all the quests in faerie, and from doing all the quests in Cornelis|
|Sellback:||Cannot be sold|
You can't get it in your inventory, so its not technically a collectable.
It is also a reference to a Rubix Cube.
It was used to summon the Hydra. Maybe there are other ancient items used to summon chaos beasts.The Runix Cube seems to be made out of Chaos Gemeralds.