Pulp City is divided into Alignments: Heroes and Villains, setting up the premise of a conflict of good versus evil.
Both of these Alignments (as well as those neutrals who straddle both camps) also encompasses a number of Factions, also known occasionally as Allegiances.
The currently known Factions with models available or upcoming are the following(click on Sub-faction name for a link to models under that allegiance):
ARC: (H/V) Ape Revolution Committee. Mutated intelligent apes and monkeys working to their own agenda.
Blood Watch: (H) heroic yet arcane mystic defenders of the city and especially Twilight Hills.
Coven: (V) villainous mercenaries making use of technology as well as esoteric forces.
Forgotten: (V) forces from ancient myth at large in Pulp City.
Grimm Under Empire: under dwelling occasional invaders.
Heavy Metal: (H) technologically orientated heroes.
Otherside: (H/V?) extra-dimensional faction.
Necroplane: (V) life-leeching villainous force from another plane.
Ulthar: (V) alien invaders.
In addition there are Heroes, Villains and Hero/Villains that belong to no Faction. Under the likes of Dead Eye and Mysterious Man this lack of Sub-faction creates an ad hoc Faction bonus for all if all are without allegiance.
It is Factions that factor into skills such as Freelancer and Merc (see this post here for discussion).