There are four types of NPC companions in the Monster Hill campaign: Allies, Hirelings, Henchmen and Followers. The use of NPC companions is encouraged by the Monster Master as small parties will likely find it difficult to survive in Monster Hill. A party size of at least six is encouraged and a size of nine is more optimal.
Allies are simply NPCs that either join or temporarily aid the party. If appropriate they will expect an equal share of treasure, modified by the Monster Master’s discretion according to factors such as the comparative strength of the allies.
Hirelings are NPCs, usually of NPC classes, that accompany the PCs for a flat charge per day, that being one silver piece for untrained hireings or three for trained hirelings including men-at-arms. In addition, hirelings going into dangerous situations will almost always require hazard pay. Typical hazard pay for dungeons will usually be 10 silver pieces per dungeon level.
Henchmen are essentially weaker adventurers that agree to work for the PCs, usually one in particular. This henchman will virtually always be lower in level than his employer. Furthermore, usually only characters of first level will agree to become a henchman, unless the employer is of much higher level. A henchman must be actively sought, they will not just show up on their own initiative and convinced to join. In addition, the PC must give an initial payment, usually of tens of gold pieces along with outfitting the henchman with equipment in most cases. The henchman will require a share of treasure, though it need not be a full one.
Followers, including cohorts, a special type of follower that is exceptional and much like a henchman in many ways, are gained with the leadership feat. The leadership feat also has a special requirement, that the character must have a stronghold or some other source of prestige, like a title or leadership of an organization.