The three (well, technically four, but the fourth is a loose coalition of city states with no unified culture, mostly aping one of the Empires to one degree or another) nations, all Empires are fragments of a single Empire that broke up in a succession war (each of the three claimants took a Grand Duchy and called it an Empire) about 8000 years ago. The Aprilian Empire is heavily elven-influenced, with very general tolerance of cannibalism, and rather inclusive sexual mores. Beyond that, they're largely Roman, with a dash of ancient Israel for good measure. Even the commoners are generally polygamous, and the society as a whole is hyper-individualist (to the point where murder is only a crime if the victim was unarmed or under the age of 14). While slavery is outlawed, the concept of "judicial slavery" exists, where a person may be sentenced to enslavement instead of a prison sentence (in this case, limited to the term of their sentence) or execution. In the former case, strict laws regulate treatment, as their enslavement is more of a lease than a possession. In the latter, no such laws exist, although social convention does keep the relative handful of owners in check. They are technologically advanced, and their magic is both widespread and highly developed.
The Markavian Empire, which controls the major mineral wealth of the continent, is much more ordered. Polygamy is extremely rare outside of the nobility, magic requires a licence, which comes with strict usage limits (casting without a license or outside of the limits of your license is a capital crime), and public possession of weapons beyond a sword, bow or knife requires a mercenary's or soldier's license. Recently, (as in somewhere in the last six months), the Empire has ceased to issue mercenary licenses, and no longer employs them, though existing licenses remain valid outside of the capital, and it is still legal to hire them for private reasons. (For various arcane reasons, it's illegal to kill a rival directly but legal to employ mercenaries to kill him and his family, raze his estates, and salt the earth so nothing will ever grow there again.) Slavery is outright illegal here, though there is a strong black market for slaves, which are generally horribly treated. The source of these is unknown, and most slaves are foreign peasants. They are the least advanced both technologically and magically, although they do have an edge in metalworking and mining.
The final Empire, Cinnabar, is aesthetically a mixture of Elizabethan England and Spain of the same era. The nation exists in a state of barely organized anarchy, with the Emperor a puppet of scheming nobles, the laws indifferently enforced, and vice beyond measure being made available by the vast trade network. Despite (or perhaps because of) this, they are immensely wealthy. Their large, well disciplined navy guards a global trade network, and anything can be bought in their markets, if you're bold enough to seek it. They are also quite advanced in many ways, largely due to their access to bits of lore from various islanders that they can put together in new ways. However, they are often quite slow to implement changes. It is believed that they were the originators of gunpowder and cannon, but the Aprilian fleet was entirely cannon armed 20 years before the Royal Cinnabar Navy managed the same feat. They are above-average in magic, and lead (admittedly almost by default) in the black arts of Demonogly and Necromancy.