In keeping with a new publisher and developer for this, the latest incarnation of the Heroes series, a completely new storyline has been developed, and with it, a new history.
Fortress: A History (From the Official Site)
The dwarves have coalesced from a series of scattered clans into a mighty nation, capable of defending itself against all enemies. Children of the Dragon of Fire, they worshipped him in the deep places of the world where magma provided the only light, and in return they were taught the secrets of the forge and the hearth.
At first, the other races were not even aware of the dwarves. Not until the Wars of Fire (28-41 ASD), when the dwarven warbands joined with the others to resist the demons, were they recognized. Once the fighting was over, they returned to their homes under the mountains and had little to do with the other races for centuries. Slowly tunnels were dug between the various dwarven cities, connecting then into a honeycomb deep beneath the earth.
All that changed when the first Dark Elves settled on the dwarves’ borders. A steadily deteriorating situation turned into the War Under the Mountain, in which the dwarves, led by Hathor Deepstrider Orlandsson, crushed the Dark Elves and drove them out. The Dark Elf dwelling places were collapsed, and the dwarves considered their borders secure.
Today, the dwarves still keep a watchful vigilance up. They watch their borders, and no one moves on their lands unseen. They befriend a precious few, and expand their kingdom carefully.
Note that most of dwarven history is actively hidden from the rest of the world. The dwarves have lengthy sagas, eddas, and histories concerning their deeds, wars, and adventures, but these are not shared with the outside world. The things they have seen and battles they have fought within their own domain remain mysterious, at least for now.
The Dragon of Fire, Dwarven Diety.
Hathor Deepstrider Orlandsson
The leader of the Dwarves during the "War Under the Mountain".
The current Dwarven "king of kings", part of the Grimsteel clan.
Thanks to ThE_HyDrA for creating and looking after the Heroes 5 section of Age of Heroes!