Frontier Worlds occupy the desperate, lawless fringes of the Imperium. Inhabitants quickly learn self-reliance by necessity, knowing that they cannot expect outside aid against marauding humans or ravenous aliens. As always, where there is little Imperial attention, heresy and mutation festers unchecked. Frontier Worlds swarm with the violent dregs of humanity, with pirates, bandits, outlaws, and worse ruling many areas. These planets easily become breeding grounds for rogue psykers, misguided heresies, and vile cults, and can threaten Mankind across the wider Imperium should their contagion spread.