The Knights of the Aurora is a Stormhost from the First Striking, like the Hammers of Sigmar and thus bear the Hammer and Lightning bolt Heraldry.
The Borealis warrior chamber of this Stormhost is led by Lord-Celestant “Arturo Boreas” sometimes riding on his Dracoth “Prism” aided by his second in command Lord-Relictor “Amortea Luminu”. They get help now and then from the Auxiliary Chamber commander: Lord-Castellant “Solarius Skygazer”, Lord-Veritant “Chiaro Scuro” and his officers Knight-Heraldor “Fulgur Halation” and Knight-Vexillor “Eos Coruscate”.
Master scout and Reconnaissance leader Knight-Azyros “Scintil Obscurea” and sky-archer Knight-Venator “Welkin Burnish” are also seen regularly between the ranks.
Rarely Knight-Questor”Solicius Dioptric” will be seen joining the army as he is mostly out on his own doing his missions from Sigmar.
Their motto: fortuna favet fortibus (Fortune favors the brave)
The Knights of the Aurora were selected based on their speed and agility. Only the best became a Knight of the Aurora. Sigmar deploys these chambers only when he sees that speed is of the essence and that it’s better to send in small but fast and effective strike forces.
When these strikeforces are being send the lightning leaves a mark on the ground where they land. Crystallizing some of the minerals above the soil.
Their first task was to secure the Realmgate to Azyr in the realm of Ghyran (Life) where Arturo single handedly cut down a ravager-lord(1).
In an attempt to liberate the enslaved continent of Beryllius, Sigmar had cast the Knights Aurora Stormhost into battle. Led by a mighty spearhead of Paladins and Judicators, the Knights Aurora succeeded in overthrowing the Bloodtyrant and his nightmarish daemon cohorts, and reclaiming two Realmgates. Alas the cost was terrible, as well over half of the Stormhost fell as casualties.(2)
References with published fluff:
(1) Age of Sigmar, Mighty Battles, p78, right hand side, 2nd paragraph;
(2) Balance of Power, p14, 4th block.