Necromunda: Core Rulebook

All of the existing miniatures are fully compatible with the new edition, so if you’ve already got a gang setup you love, you can just pick up the Core Rulebook separately. You’ll also need one of the new Gang books too, as each contains all of the updated rules for your faction(s) of choice.

Gangs of the Underhive contains rules for House Cawdor, House Delaque, House Escher, House Goliath, House Orlock, House Van Saar, Palanite Enforcers, Venator Gangs, and Corpse Grinder Cults, as well as rules for Justicar Courts, Hired Guns, Brutes, Hangers-on and Pets. 

Meanwhile, Gangs of the Outlands contains rules for Outcast Gangs, Free Ogryn Gangs, Genestealer Cults and Genestealer Corrupted Gangs, Chaos Helot Cults and Chaos Corrupted Gangs, Malstrain and Malstrain Corrupted Gangs, Spyre Hunting Parties, Ironhead Squat Prospectors, and Ash Waste Nomad Gangs, along with the same Hired Guns and Brutes, Hangers-on and Pets from the other book.