Source: nation names and page numbers follow Illwinter's official Dominions 6 manual. Each summary is my shortened version of the corresponding introduction.
Arcoscephale, Sibylline Guidance
A diminished but enduring human kingdom follows the prophecies of Sibyls, fielding archaic infantry, elephants, cavalry, and mages with wide magical access.
Phlegra, Sleeping Giants
Human slaves rule themselves while monstrous giants remain imprisoned below, but younger Cyclopes already serve as soldiers and smiths as the old terror begins to return.
Pangaea, New Era
The woodland realm has adapted to a changing world, combining minotaurs, centaurs, satyrs, sacred dryads, and heavy centaur cavalry under nature mages.
Pythium, Serpent Cult
The faded Emerald Empire has embraced a serpent cult, pairing heavy legionnaires, serpent cavalry, gladiators, and sacred hydras with varied but mostly modest magic.
Lemuria, Soul Gates
The dead of old Ermor pour through opened Soul Gates, forming an immortal priesthood and spectral legions sustained by a population-killing dominion.
Man, Towers of Chelms
A mature feudal kingdom defends its towers with longbowmen, crossbow infantry, knights, and Wardens while learned mages preserve air, earth, and astral traditions.
Ulm, Black Forest
After civil war and a great malediction, Ulm is ruled from the Black Forest by secret orders, blood mages, and vampires supported by infantry, knights, and ghoul guardians.
Agartha, Ktonian Dead
The Pale Ones are gone, leaving human cave-dwellers to command their dead Oracles, animated statues, heavy infantry, and powerful earth-death magic.
Marignon, Conquerors of the Sea
The old theocracy has become a seaborne imperial power whose sailors, crossbows, flagellants, inquisitors, and blood priests carry fiery faith across the oceans.
Abysia, Blood of Humans
Humanbred descendants now dominate a fading Abysia, retaining fire resistance, disciplined infantry, axe throwers, and the old kingdom's fire and blood magic.
Ragha, Dual Kingdom
Abysian-descended Turans and winged Airyan refugees share a seasonal monarchy, blending fire and ice, gryphon cavalry, flying troops, and both nations' magical traditions.
Caelum, Return of the Raptors
The Raptor Clan has returned to prominence among Caelum's winged peoples, bringing earth and death magic to fast archers, ice troops, and mammoths.
Gath, Last of the Giants
The last Gittite giants rule alongside several human tribes, fielding mighty sacred warriors and mages of fire, earth, astral, blood, nature, and death.
Patala, Reign of the Nagas
Naga kings now rule the ape lands, joining sacred amphibious serpent warriors with monkey infantry, missile troops, and strong water, earth, nature, and astral magic.
T'ien Ch'i, Barbarian Kings
Khans have seized a crumbling Celestial Empire, adding cavalry and mounted warfare to its heavy infantry, archers, celestial summons, and broad magical tradition.
Jomon, Human Daimyos
Human rebels who overthrew Bakemono rule through rival Daimyos, fielding samurai infantry, archers, cavalry, ninja assassins, and many national summons.
Mictlan, Blood and Rain
Atlantians have joined Mictlan's rain cult, adding sacred amphibious warriors and water magic to its light troops, blood sacrifices, and Jaguar and Eagle Warriors.
Xibalba, Return of the Zotz
The bat people have reclaimed their caverns, mustering swarms of stealthy fliers and a few amphibious Muuch under water, death, earth, and blood mages.
C'tis, Desert Tombs
The old swamps have become desert and the lizard kingdom now marches with reanimated dead, undead priests, and powerful death and fire magic.
Midgård, Age of Men
Humans have inherited Vanheim while a few Vanir remain, combining heavy infantry, sailors, skinshifters, berserkers, and masters of air, astral, and blood magic.
Bogarus, Age of Heroes
A cold human principality descended from Vanarus fields cavalry, mounted archers, and infantry while its learned mages command an unusually wide range of magic.
Utgård, Well of Urd
Humans now share the old giant realm with remaining Jotuns, combining giant and human infantry with water, astral, death, glamour, and blood magic.
Vaettiheim, Wolf Kin Jarldom
Small, stealthy Vaettir have founded their own cold jarldom, riding wolves and serving alongside a few giants under death, glamour, nature, and blood mages.
Feminie, Sage-Queens
A hidden Amazon queendom freed from Ind fields sacred human infantry and knights beneath sage-queens whose dominion conceals the realm's borders.
Piconye, Legacy of the Prester King
Small horned people once subject to Ind now defend their own kingdom with Bird Knights, sacred crossbowmen, strong priests, and astral-earth magic.
Andramania, Dog Republic
Civilised Cynocephalian dog-men have built a disciplined republic whose conscript infantry and crossbowmen fight under mages of fire, astral, nature, and earth.
Pyrène, Cambion Kings
Cambion dynasties rule a feudal mountain kingdom of cave-descended humans, crossbowmen, knights, and sacred demon cavalry supported by blood and glamour magic.
Erytheia, Kingdom of Two Worlds
A marriage between Pelagian and Arcoscephalian colonies created a realm spanning land and sea, with amphibious mermen, Tritons, humans, and broad elemental magic.
Atlantis, Frozen Sea
Exiled Atlantians have settled an icy coast, becoming ocean-sailing amphibians armed with magical ice polearms and supported by water and death magic.
R'lyeh, Dreamlands
Alien Starspawn and Illithids rule an underwater slave empire of Atlantians, hybrids, and summoned Void beings, spreading insanity through astral and dream magic.