Just like how @Wario100 said they were the zombies in his NLBTWWAIOF, in mines they are the negative copies of the original positive numbers. Their mission is to take out their original counterparts and were always mean in the start because they're basically the opposite of their personalities. (They're not canon in the original series.)
Cedits to Everyone, especially Mike Salcedo and Geoff for Number Lore.
