This quest will begin automatically after you have spoken to Brutus Plutocratio at the end of the quest The Escaped Slaves, with Spartus Spartacio and the other four slaves becoming hostile and attacking you. Kill Spartus and the four Rebelling Slaves, then talk to Brutus Plutocratio for your reward.
That was Spartus Spartico. What an ungrateful Human! I had him trained as a bodyguard, but what does he do? He escapes and gathers warriors around him to kill me. Thanks for your help. Here's some more gold.
Easter Egg: The leader of the rebelling slaves in this quest is called 'Spartus Spartacio' - Spartacus, according to Roman historians, was a slave and a gladiator, and a prominent figure in the slave uprising known as the Third Servile War.