Robloxians are creatures common to various realities that connect to the Nullscape. While they are one of the more diminutive entities in the Void, they are also one of the most resilient. They are not only highly intelligent, but they are capable of respawning -- coming back after death.
Due to the nature of their worlds, Robloxians also have the ability to traverse small pockets of the Void. What particular abilities they have depends on the world from which they come, or the strength of their personal expression.
When respawning, Robloxians leave behind a corpse. It is easier for corpses to become voidbound on account of no longer having a will of their own, however, voidbound corpses, Husks, still burn with the desire of their past selves to escape the Void. So, through mindless determination, they chase after a flame which exists in another body.
Currently, the Voidbreaker is the only known instance of a living Robloxian that became Voidbound.
Robloxians bear some form of resistance against becoming voidbound as each time they die, it's like the amount of Void exposure they received is reset. The Voidbreaker then, has either gone a long time without death, or perhaps there is a small amount of Void exposure that remains even after death.
While the Voidbreaker hasn't fully succumbed to the madness of the Void and is intelligent enough to understand Robloxian speech, they do not seem interested in making peace. As such, they are marked as an unstable entity.