Castus was a Gallic gladiator, and escaped from the gladiatorial school of Lentulus Batiatus in Capua. Together with the Thracian Spartacus, and the fellow Gauls Crixus, Oenomaus and Gannicus, he became one of the leaders of rebellious slaves during the Third Servile War (73-71 BC). He was killed along with his co-commander Gannicus and their Gallic and Germanic followers by Roman forces under Marcus Licinius Crassus at the Battle of Cantenna in Lucania in 71 BC.