Avoirdupois: The House of horses, chivalrous and austere, with a history of strong religious convictions. Their army is the strongest in Calabria, though their hesitance to modernize might spell their downfall.
Bisclavret: The House of wolves who cast off their traditional roots to claim the resource-rich woods, giving them control over lumber production (and subsequently, shipbuilding). They are for the moment the House most interested in progress and innovation.
Doloreaux: The House of boars, beset on all sides by rival Houses and with only enough farmland to subsist, is the most aggressive of all Houses. The official religion is the worship of a fertility goddess and, naturally, the clergy is all female.
Rinaldi: Greatest of the Great Noble Houses, the grey foxes count the High King of Calabria as one of their own. They rule from the city of Triskellian, the greatest of all cities and the origin of the continent's biggest religion. Sadly, their titles are hollow and their rule is wavering. The true powers of the city are the Guild Masters. Still, the House basks in their remaining power and plays at still being relevant.
Apart from the Great Noble Houses and their vassals, two other forces lay claim to territories in Calabria:
Phelan: These are the wolves who continue to keep their old ways, the five clans continuing to live as their great-grandfathers did. To outsiders, this is a land untouched by civilization and fraught with dangers. They even say that goblins known as the Morrigna live in these dark woods.
Chevernaise: Goat-tribes who inhabit and lay claim to the Rothos Mountains, something that infuriates the Doloreaux to no end.
The players take the role of adventurers plucked from the new middle class. They have esoteric skills and abilities above the common unskilled laborers, and have access to expensive equipment. Meanwhile, the nobles of Great Houses fight their petty wars for more power, and are not above using those below them as pawns in their game. The world is waking up to an Age of Reason where technology is slowly catching up to magic and the old ways of government are being questioned.
Ironclaw Provides Examples of:
Animal Stereotypes: Each of the species detailed have their own quirks and stereotypes. Note that these are In-Universe examples of stereotypes, as well; the Species Descriptions are largely how the other species see each other.
Armadillos: Tough-skinned pacifists with a penchant for introspection.
Badgers: Artisan homebodies. The most stable of the mustelids.
Badass Creed: Every character is supposed to have a motto that describes their outlook on life. Acting out according to said motto earns you more experience points.
Black Speech: Semi-subverted. Night Speech is an ultrasonic language that can only be spoken by Bats (who can echolocate), though other races with "Keen Ears" can learn to understand it. Though not an inherently evil tongue, due to the bats' reputation, others treat it as such.
Carnivore Confusion: Subverted. Ironclaw and Jadeclaw took a page from Usagi Yojimbo and introduced an entire ecosystem of lizards, dinosaurs, and lizardy birds which fill the usual niches of livestock, beasts of burden, pets, and wildlife. Pests include both small lizards and oversized insects; Word of God has mentioned beetles the size of cats.
Chunky Salsa Rule: If you score an overkill (or are subject to one), the result is being so horribly mutilated that allies will become afraid. There's also not enough left for Necromatic spells requiring corpses to work on the victim, and not enough for the game's only genuine resurrection spell to work fully — it can resurrect them, but they're too badly mangled to be restored good as new and are permanently disfigured.
Critical Failure: If you have a D4 in a skill, you are likely better off not using it at all.
Metaplot: Subverted. The first published adventure and the first tie-in novel deal with the murder of the High King and most of his family, and the search for the sole surviving heir. It became the common touchpoint for almost every campaign using the official setting — but every campaign resolved it differently, with far-reaching impact on the rest of the political situation. (It also immediately established Ironclaw as a game where beginning characters can be kingmakers.)
Mysterious Animal Senses: Each Species in Ironclaw has one or two Natural Senses, but no more; when using those senses, they can include their Species Trait in their Observation roll. Some Species have Gifts that improve those sense even further (Keen Eyes, Keen Ears, Keen Nose), or provide exotic sensory abilities like Echolocation.
Shout-Out: the cover of the first edition was a deliberate homage to Slayers, with Lina and Naga as a Fox and a Wolf.
One sample character, a vixen warlock known as the "bandit killer" is a continuation of the above; it's more obvious in the first edition where the character is Lina in all but name and species.
There is Mount Eisengrim, named after Ysengrim the wolf of the Renard Cycle.
The Bisclavret are named after a 12th Century French poem of the same name. It's about a werewolf.
Shown Their Work: particularly noticeable with the Phelan, whose culture is based heavily (and accurately) on pre-Christian Celtic society. The Phelan calendar is based on the actual Celtic lunar calendar, and the Druids are much closer to the priestly caste of history and the mystics of folklore than to the nature priests of modern fantasy.
Sliding Scale of Anthropomorphism: codified in the game mechanics. The Race Trait (Species Trait in Second Edition) is an attribute that ranges along the same scale as Body, Mind, and the rest, and indicates just how strong your animal heritage is. There's no direct connection to physical appearance stated, but the art suggests that the inhabitants of Monderévelé range from Type 1 to type 3, with "Atavists" who tread the line into Type 4.
Stealth Pun: The Avoirdupois are well known for their Chivalry. Cheval means horse
Talking Is a Free Action: You can talk freely on your turn, but you'll have to wait until the other person's turn for them to reply. Talking may be free, but a conversation is not.