Here's the fluff I've been working on for my Lizards in AoS:
The Exodus Engine my lizards were on ended up in Ulgu, the realm of shadows. Lord Malzareth, unlike most of his peers, decided not to land his exodus engine, and the city/settlement remained within the shadowy clouds of Ulgu for millenia, only dropping below the magical clouds to to seed the Black Forest (more of a jungle, really) below the city with the creatures that the lizardmen brought from the old world, and to retrieve new beasts when they needed them. Malzareth watched the as the races of the world-that-was settled the realm of shadow. This pleased him, but he saw no reason to reveal the presence of the city and risk conflict, as the city was small, and the spawning pools had been rather inactive since the death of the old world.
Then, chaos returned.
Again, Malzareth simply watched as the realm was overrun by the forces of chaos, namely followers of Tzeentch and Skaven of clan Eskerin following a vermilord deceiver known only as 'The Shadow-kin.' Around this time, Oxotl arrived in the city with a dozen bands of chameleon skinks. They came before Malzareth and asked his permission to use the city as a base from which to launch raids on the forces of chaos and protect those of the lesser races that they could. Malzareth had wanted to confront the forces of chaos, but had not the saurus to do so in open battle. As such, he agreed to Oxotl's plan, and gave him the use of the city's few chameleons and their sizable force of terradon riders.
Over the next few millenia, Oxotl would lead countless attacks against the forces of the Shadow-kin and the Harbringers of light, a Tzeentchian warband obsessed with discovering everything there was within the realm of shadow, and with subjugating it's people for its leader's vile magical experiments. The city remained within the high clouds of Ulgu, undetected by the forces of chaos aside from the odd furry or screamer which would stumble upon the city and be swiftly destroyed by the flights of terradon and ripperdactyl riders who flew constant patrols around the flying fortress. And so things remained, until the arrival of the stormcast eternals.
A party of chamelion skinks, led by Oxotl himself, was scouting out a skaven nest near the Black Forrest when a blast of twin-tailed lightning struck down from the heavens and deposited a force of armored giants the size of saurus, clad in burnished steel and green colored armor, and wielding gleaming warhammers. In moments, over half of their number took to the skies on wings of light, flying off to scout out the surrounding area, while the rest secured the immediate area, shields raised and hammers at the ready. Oxotl watched the warriors, and sensed that they had an aura of honor, of order, of good. He was considering approaching the warriors when they were set upon by swarms of night runners. The warriors fought valiantly, but one by one they were overrun, their fallen bodies vanishing in brilliant flashes of light when struck down. Eventually, only one remained, and it was subdued by the skaven and carried back to their nest. Oxotl decided to try and rescue this strange creature, and so led his band into the warren. They sneaked in, killing sentries and guards as they passed, before eventually finding the strange creature chained to a wall, being interogated by a grey seer. Oxotl shot the seer with a dart containing a particularly nasty poison, then freed the strange creature, who retrieved its shield and hammer from an adjoining room as the alarm was raised. Together with their new ally, the chameleons and Oxotl fought their way out of the warren and fled into the jungle. There, he led the warrior to a gateway, much like a realmgate, which transported them to the floating city. Once there, the newcomer was taken before Malzareth.
The Slann reguarded the warrior, and asked her name. She Replied that her name was Yvera, and that she was a liberator prime of the Banehammers chamber of the Daughters of Sigmar stormhost, and demanded to know where she was. Malzareth humored the eternal, sensing that she was a kindred spirit to the seriphon, and told her of the city and its inhabitants. He asked if more of her kind would come. She said yes, that the force she came with was just the vanguard, and her sisters would soon arrive in force. So, for the first time in many thousands of years, Lord Malzareth left his temple, in order to meet with the stormcasts and arrange some sort of alliance.
He left with the full force of his temple guard, in addition to the city's remaining saurus and many skinks and terradon riders, plus Oxotl's chameleons. They left the same way they entered, and the slann subtly errased the knowledge of how to get to the city from Yvera's mind.
When the seriphon and the ayward libereator arived at the staging point, they found a pitched battle in progress. The Banehammers had engaged the skaven from the warren and were in danger of being overrun. Yvera charged immediately, desperate to help her sisters, and Malzareth ordered the saurus to follow. With a flank charge from a horde of saurus, plus attacks from above by the teradons and the assassination of the clan-leaders by Oxotl and his followers, the battle was decided quickly.
Malzareth met with the Lord (or in this case, Lady) celestant of the Banehammers, Morticia Demonbane. She thanked the slann for his aid, and for rescuing her warrior. Malzareth did not reply to the thanks, saying only this: "You are not alone in this realm. When you need aid, we will come. We will be watching. Good luck, eternal." And the whole army vanished in a flash of celestial magic.
Since then, the Banehammers have been assisted by Terradons and skinks in many battles. These warriors never stay for long though, always vannishing at battle's end. It really matters not to the eternals, who were simply glad to have an ally in this dark and gloomy realm. And all the while, Malzareth covertly guides the eternals through the realm towards the Ayr realmgate. For what reason, none but him know.
When they fight together, I call it a celestial alliance, due to the whole lightning blood thing. I'm planning on getting some stormcast, so I came up with this. I also wanted to take advantage of the fact that stormcast can be male or female, and make the first all-female stormhost.
(Edit: Shit, I just realized how long this was. Jesus...)
