Tamriel Rebuilt is an ambitious mod project that aims to add the full mainland of Morrowind to The Elder Scrolls 3: Morrowind, which was set on the large island of Vvardenfell. It's been in development for a whopping 20 years now. The last we heard from the team was via an updated development roadmap in late 2021, but today the developers released a new update that adds two major new regions to the game world: Dominions of Dust, and Embers of Empire.
Dominions of Dust is centered on the House Hlaalhu trade port of Andothren, which sits southwest of Vvardenfell on the Inner Sea. The sparsely populated but dangerous borderlands to the west of Andothren are contested by Hlaalu and their rival, House Redoran. The region is also home to the peaks and valleys of the Velothi Mountains, once a stronghold of the long-lost Dwemer, while Clan Ishanuran continues its nomadic ways in the Armun Ashlands to the south, an area devastated by the eruption of Red Mountain.
Embers of Empire is a complete overhaul of the western shore of the Telvanni peninsula, and includes the last remaining symbols of Imperial power in what is the most hostile region of Morrowind: The settlements of Firewatch and Helnim, and the outpost of Nivalis on the island of Althoa, one of the few surviving navy forts in the region.
Between them, Dominions of Dust and Embers of Empire add two new Ashlander clans and a joinable vampire clan called the Orlukh, more than 200 new or reworked quests, and offer a land mass triple the size of the Morrowind expansion Bloodmoon. There are also "many hundreds of bugfixes and consistency improvements to our older content, including major improvements to exteriors, interiors, and assets, as well as several new quests in our older areas."
This map lays out the location and scale of the new additions:
It's a truly impressive addition and the new cities look fantastic, but work on the Tamriel Rebuilt mod is far from over: The number of quests in the mod is now roughly equivalent to that of Morrowind and its expansions, but the development team said that only about half of the mainland is currently playable. According to the updated roadmap released in 2021, Dominions of Dust and Embers of Empire will be followed by Thirr Valley, a Hlaalu-dominated region to the southeast of the Dominion of Dust, the Sundered Scar region east of Old Ebonheart, and then the desert highland area of Shipal-Shin just south of Thirr Valley.
So yes, all very ambitious, but after 20 years of work—and plenty to show for it—I don't doubt that it will happen. The Tamriel Rebuilt mod, installation instructions, and other supporting files can all be had at tamriel-rebuilt.org.