30 Warriors -- Freemen and Captives -- to populate your arenas.
30 cult members, of varying levels of sanity and skill. Divided into Guilds for convenience and clarity. Could potentially be used as 30 gang members, depending on your needs.
Draw the party together as debtors to the local lord, king, head of the thieves guild, or mercenary clan, who is forcing them to work together to pay off their debts.