It is said that in the Age of Myth seafaring humans from the Realm of Light created a city of such splendor that the Gods of Chaos themselves could not gaze directly upon it. This city was said to have had towering stone walls and fleets of ships sailing on the glittering seas of Hysh. The inhabitants of the city named it Helios, city of the radiant dawn, after its warm weather and unusually long days. The Heliosi were a fair-skinned folk with a propensity for sailing and ship-craft, their long sleek sandalwood ships patrolled the coastal waters of Hysh weeding out the forces of Chaos wherever they were found. At the end of the Age of Myth, Sigmar retreated to his fortress-city in Azyr and abandoned the remaining peoples of the Mortal Realms to the depredations of Chaos. After successive waves of Chaos invasions Helios eventually fell to ruin and although the city was brought low many of the surviving Heliosi fled into the surrounding country side and into hiding. For an age the descendants of the Heliosi eked out a living in the ravaged lands of Hysh, carrying on the memories of their former glory.
At the end of the Age of Chaos, Sigmar returned to the Mortal Realms seeking to repulse the Chaos invaders and restore order and civilization. When his army of Stormcast Eternals finally reached the Realm of Light he found the descendants of the Heliosi and although they had regressed into a primitive warrior culture from necessity, they had preserved the traditions of their elders, honoring martial prowess, justice and sailing skill. The successive generations of Heliosi had stood firm against Chaos and ultimately succeeded in surviving. It was ultimately the endurance and grit of the Heliosi that convinced Sigmar to rebuild Helios. Sending his best Freeguild Engineers and members of the Collegiate Arcane, Sigmar returned Helios to its former prestige. It was this act of kindness that led to the Heliosi swearing allegiance to Sigmar and his Stormcast.
Helios has once again become a bustling hub for trade and life in Hysh, her warships patrol the coasts once more and her soldiers, The Sun Legion, defend the city and the outlying areas from bands of roving beastmen, sea monsters and other threats. The city is also home to the newly opened White College, a school for the learning and mastery of the magic of Hysh. The College is based on the Celestial Colleges of Azyrheim and maintains an order of White Battlemages, ready to support and empower the Sun Legion with auras, enchantments and offensive magicks. Helios is also home to a brotherhood of Vanguard Stormcast on permanent duty, sent by Sigmar to assist in the defense of the city. In more recent years the city has witnessed the return of the Kharadron Overlords, establishing trade ties with the sky-city of Barak-Zilfin. Although the duardin prove to be mercurial tradesmen they make for staunch allies and loyal friends.
The areas surrounding city have been mostly cleared of Chaos taint but the warriors of the Sun Legion have discovered two realmgates in the surrounding islands that they constantly maintain vigil over, lest the forces of Chaos exploit them to invade Helios and Hysh at wide.