The caste system was a rigid social hierarchy installed on Cybertron following the disappearance of the Primes. The caste system was overseen and administered by the Guilds of Cybertron. It was at Fort Scyk that the first generals of the High Council's militias first conceived the idea of formalizing the formerly loose-knit castes. Sentinel Prime was a major proponent of the system and played a large part in its evolution and adoption as an absolute, mandatory social authority.
Though its rigid structure was intended to preserve Cybertronian society, its repressive force was a large factor in the social decay and unrest that led to the formation of the Decepticons and the start of the Great War.
Under the caste system, a Transformer was assigned to a caste by the Guilds at the moment they emerged from the Well of All Sparks; these assignments were immediate and absolute. Known pre-war castes and their place in the social hierarchy:
- Low castes
- Industrial workers and miners
- Middle castes
- Building and civil engineering
- High castes
- Castes of unknown level
- Data Caste
- Cultural investigator
- Programming Caste
- It is known that the Data Caste is higher than that of industrial workers, it is likely one of the middle castes from the way it is described, but this is not said outright. The Cultural Investigation caste is, again, higher than the Data caste but whether this makes it part of the "High Castes" or simply "higher" within the middle caste is unknown.
- It is mentioned each Cybertronian is taught to assume their most natural alternate mode and then assigned to a caste. However, it is seemingly arbitrary whether one tank becomes a soldier while another becomes a miner... which is the point the Decepticons were making, really.