"The empire of Shurima was once a thriving civilization that spanned an entire continent." Riot's overview opens in the past tense and stays there for three paragraphs, through the god-warriors who built it, the rebels it crushed, and the failed Ascension that "left the capital in ruins". Then, at the end, the tense changes. The emperor is back, and the city is standing.
This is the hub for Shurima: what it was, what the Sun Disc did, what came of it, who lives in the sand now, and what the southern continent would be in the Riot MMO. The game parts are speculation and labelled. The rest is Riot's.
What Shurima was
An empire that covered the southern continent, "forged in a bygone age by the mighty god-warriors of the Ascended Host", which "united all the disparate peoples of the south, and enforced a lasting peace between them". The overview does not pretend the peace was gentle: "few dared to rebel. Those that did, like the accursed nation of Icathia, were crushed without mercy."
Its capital, also called Shurima, stood under the Sun Disc, the artefact that made the Ascended. When the last emperor's Ascension failed, the city fell, the disc was buried, and "tales of the empire's former glory became little more than myth". The Sun Disc is the region's landmark on Riot's interactive map, and the Buried Sun Disc, painted for Legends of Runeterra, is the cover of our article on the game's release date, why "before 2030", and not sooner, for reasons of mood rather than lore.
What the Sun Disc did
It made gods. Ascension was a ritual, performed under the disc, that raised a mortal into something more: Nasus and Renekton, brothers and scholars, became the jackal and the crocodile; Azir, the emperor, was meant to follow. His Ascension was sabotaged by Xerath, a slave and magus who took the ritual for himself, and the failure destroyed the city.
The Ascended are the reason Shurima matters beyond its borders. They defended the world against the Void, which entered it at Icathia in the empire's south-east; some of them were later corrupted and became the Darkin, the weapons that carry Aatrox, Varus, Rhaast and the rest. Every one of those stories begins under the disc, which is why we say in playable races that the Ascended and the Darkin are events, not species.
What came back
Azir returned. The lore places his rebirth in the present, tied to Sivir, a mercenary who is his descendant, and with him the capital rose from the sand. Riot's overview describes today's Shurimans as nomads among the ruins; the ruins are now a city with an emperor in it, and the desert's politics have changed in a way no other region's have. Xerath is free as well. Renekton, imprisoned with him for centuries, came out mad. Nasus is trying to hold what is left.
Beyond the capital, the continent has its own places and peoples: Nazumah, the city K'Sante defends, which never bowed to the empire; the stoneweavers of Taliyah's tribe; the Sentinels of Light, of whom Akshan is one. Ixtal, in the east, was one of the first nations to join the empire and has been sealed since; it has its own page on Riot's map and in the 13 regions of Runeterra.
Who lives there
Riot's roster, eleven strong: Akshan, Amumu, Azir, K'Sante, Naafiri, Nasus, Rammus, Renekton, Sivir, Taliyah and Xerath.
The empire: Azir, Nasus, Renekton, Xerath, and Sivir, the heir who did not want to be one. The continent: K'Sante of Nazumah; Taliyah, who moves stone; Akshan, the Sentinel with a grudge. The old things: Amumu, a mummy who has been sad for a very long time, and Rammus, an armadillo the desert worships. The Darkin: Naafiri, a dagger that runs a pack of hounds.
The places
The capital and the Sun Disc; the Oasis of the Dawn; Nazumah; the tombs. Legends of Runeterra gave Shurima 238 illustrations, second only to Bandle City, and the largest set of landmark cards of any region: the Buried Sun Disc, the Emperor's Dais, the Sandswept Tomb, the Preservarium, and more. No region in the setting has been painted in more detail from more angles.
Shurima in the MMO, as a guess
A reading, not a report. Riot has confirmed the setting and nothing about which regions ship, or how.
Shurima is the game's end-game by any reading. It is another continent, its history is the deepest in the setting, its ruins are the genre's favourite kind of content, and its bosses are the ones we list in Riot MMO raids: the Ascended, the Darkin, Xerath, and the Sun Disc itself. A player who has learned the three western regions and sailed to Ionia arrives in Shurima to find out where all of it came from.
It is also the region whose present is most in motion. An emperor returned within the lore's living memory is a world-changing event of the kind MMOs stage as expansions, and Riot's era choice, the question in when is the Riot MMO set?, decides whether the player finds the city standing or watches it rise.
What we do not know
Whether Shurima ships at launch or as a later region.
Whether Azir's empire is a faction, a quest hub, or a threat.
Whether the Sun Disc can be used in the game, which is the question the lore's every tragedy turns on.
For Shurima among the other twelve regions, with the numbers, see the 13 regions of Runeterra.