|Battle Cry||"I Shall Defend!"|
|Strength||Unknown, Assumed full strength|
|Specialty||Fuck Hueg Armored Assaults, Having more tanks than you|
The Aurora Chapter is one of the many successor chapters of the Ultramarines produced during the second founding; they specialize in massed armored assaults, and are reputed to have more Land Raiders and Predators than any other chapter in the Imperium. They have been involved in a number of campaigns, in recent note the Zeist Campaign against the Tau. Having more tanks than God requires having a sufficient source of parts and ammunition, and so the Aurora Chapter has their home world of Firestorm, which is a forgeworld so capable it can rival the output of several high profile Mechanicus worlds combined. In effect, the planet can be considered the Chapter's forge, with a large percentage of its output diverted to supplying the Chapter.
According to Forge World's Horus Heresy books, they are likely to be descended from the Ultramarines' 4th Chapter, the "Aurorans". It's noted that even during the Great Crusade, they had five times as many armored vehicles as a typical Chapter in the Legiones Astartes (and keep in mind that this was when the Iron Hands were still at full strength and would also be skewing the numbers).
They are mentioned as having a feud with the Knights of the Raven chapter, after having taken unacceptable losses while fighting alongside them; this was further exacerbated when the Aurora Chapter accused the Knights of the Raven of cultivating superstitious heresy on their own homeworld of Coralax (though this seems absurd since there are so many chapters with feudal/feral backgrounds, so it seems a bit petty that any other chapter would care), when the Knights took insult at the obviously inflammatory remarks, the two chapters came to blows with each other. The issue was only resolved when Marneus Calgar stepped in and quietly mentioned that the Knights of the Raven should go on a penitent crusade, which they did.
Once upon a time, the tread heads lost a beloved Land Raider in the xenos/heretic infested Jericho Reach. The Deathwatch recovered the tank, but found it to be beyond repair; however, knowing the Aurora Chapter had a massive piercing hard-on for their tanks, they decided to do their battle-brothers a solid by taking its main axle and reforging it into a thunder hammer by the name of Remembrance. It was thought that doing this would allow the destroyed machine to avenge its destruction, and every marine that has wielded the weapon in battle swears it strikes with the force of a tank, which is Awesome.
There is also some discrepancy about the chapter's numbers. In 3rd Edition, they were cited as having over a thousand predator tanks alongside the rest of their sizable tank force; however, in 4th edition and later this is scaled back to more Predators and Land Raiders than three chapters combined (the Heresy Era Aurorans had more than five times that of a normal chapter). So, if you take the current disposition of the Ultramarines as an approximation of a "normal chapter", that gives the Aurorans somewhere between 75 and 125 Predators and 30 and 50 Land Raiders.
Despite their predilection for massed tank combat alongside their typical battle contingents, they aren't hinted at being massively divergent from the Codex Astartes, which is normal - the Codex organisation doesn't have listed numbers of vehicle drivers in their armouries; many are assigned as required from the 6th or 7th Tactical Reserves and likely return to their company duties when their vehicle is not selected for a mission. Some individuals may exist permanently attached to the chapter's armoury and come to specialise in armoured operations and are commonly associated with larger or rarer vehicles. The Aurorans may indeed have more of these specialists than any other chapter commensurate to their greater number of vehicles. In the 5th Edition codex, Antaro Chronus was said to have command of fifty brother-marines, though this likely includes both the permanent armoury staff and transitory vehicle operators when they are called to ride to war. Using the three times rule, we can extrapolate that the Aurora Chapter have around 150 vehicle operators in various positions around the companies and from the armoury itself, meaning they may have more tanks than drivers.
Alternatively, (though there is no evidence to support this whatsoever since no other Codex Chapter does this) Their large vehicle pool could be maintained by either having their serfs man the tanks or perhaps using aspirants for it. The Aurorans would no doubt desire aspirants who are talented in armored warfare. If so, this may well be one of the most effective Chapters as they would be capable of leveling Great Crusade level armored support in addition with fielding all of their Space Marines without wasting any crewing vehicles (other than rare ones like Land Raiders). If not, then they are among the most moronic of Chapters as the whole reason Predators and such are used instead of Leman Russ tanks is because the Space Marines are practically walking vehicles anyway and something fast to provide support around the battlefield wherever needed is what the Space Marines most often require.
More realistically, since Astartes already generally rely on small elite surgical strikes rather than thundering vehicle formations, having flexible vehicles with small crews that can help fill in the Devastator (and to a lesser extent Tactical) role. In all likelihood these guys keep many of their vehicles stored as spares and deploy different amounts of them depending on the need and use for them, which is how most chapters operate anyway. Orbital assets, scouts, and fast attack elements would make it a priority to target anti-armour forces (and so would the vehicles themselves), which they kind of already do since small arms tend not to bother Astartes too much, and they tend to have valuable goodies they can't really afford to replace.