Hive Fleet Colossus
Hive Fleet Colossus is a small Tyranid Hive Fleet first discovered in the Eastern Fringe.
Chronological problems of Colossus
Hive Fleet Colossus is one of the oldest hive fleets mentioned in the fluff, not only because (in theory) they are one of the oldest Tyranid fleets around the galaxy, but because they are one of the earliest mentions of Tyranids by GW as a whole. As such, there are problems with a decent amount of their lore. In theory, the first sightings of Hive Fleet Colossus were around M28, between the Ultima Segmentum and the Segmentum Tempestus. This fact alone brings up tons of problems.
First, the Great Crusade didn't start until M30 (the conquest of Luna being around 780.30M), so we don't really know how we could know about them so early if the Imperium wasn't even around. It could be a case like Hive Fleet Ouroboris and just have rumours or legends from the isolated human worlds about beings similar to the 'nids, and then imperial authorities just gave the hive fleet the same name as the menace from the old tales afterwards. If Colossus had been discovered by xenos first, there would be some sort of record of that in the hands of one of the biggest factions in the galaxy who would care (either the Necrons or the Eldar), because otherwise, no other superpower could've organized enough forces to destroy a full hive fleet and it would have devoured the entire sector.
Second, if the dating of Colossus's sighting is remotely true, that means a Hive Fleet has been going around a pretty big area of the galaxy and it has somehow not eaten enough planets to avoid being destroyed by the Imperium in M41 (we'll get to that later). We could say the Eldar could've campaigned against it, like they did with Hive Fleet Naga, but there are no records of something like that ever happening.
Lastly, if Colossus really did come in M28 and somehow stuck around until M41, how come no one said anything until Behemoth arrived? The Imperium of Man conquered the area during the Great Crusade, the Eldar were around before that, and other multiple minor xenos species were living there too, however none of them did anything to deal with Colossus. It couldn't have been dormant and hidden, because if it had, we wouldn't have those reports confirming its discovery in M28. Tyranid activity is not generally known for being subtle. Someone must have known and someone must have done something to avoid Hive Fleet Colossus's growth.
That's just the chronological problems. We have to get around other things as well.
Singularities of Hive Fleet Colossus
Hive Fleet Colossus's bio-ships don't seem to be like the rest of the Tyranid fleet. Instead of being fully made of organic materials, Colossus's bio-ships appeared to be made out of rock and stone, with the organic part on the inside like some sort of hermit crab.
Also, Hive Fleet Colossus was recorded to use a particularly interesting organism for their means: a race of sentient, centaur-like beings, most likely the Zoats. This species was supposedly a product of the Hive Mind and were a race of sentient beings that could use mechanical technology, had some level of sentience and intelligence and were used as slaves by the Tyranids. They were even capable of comunication through psychic means like telepathy, and most experts thought they were used as envoys or ambassadors in service of the hive fleet. These creatures could be fused with Tyranid symbiontes, which could allow them to use some tyranid bioweaponry, allowing them to act as soldiers. However, the passing of time and the evolution of the lore made this particular element irrelevant: The image of the 'nids as a massive swarm united by a singular Hive Mind doesn't mix well with the zoats, and their role as ambassadors or slaves was made irrelevant by the creation of other bioforms, like the genestealer for infiltration and sabotage. Also, the players didn't like this unit that much, so GW decided to erase them from the game. The zoats are usually said to have been eaten by the Tyranids in a futile attempt to escape from their grasp, after the Hive Mind realized individual consciousness and sentience were not that useful compared to an unified mind. Thus, they were eaten by the 'nids, just like the Squats, and now they are almost (if not entirely) extinct.
Also, these centaur-like creatures are the sources of the rumour saying the Tyranids are running away from something even scarier than them. But, considering that the ones saying that were the Zoats, and the influence of the hive fleet was questionable, maybe they were referring to the Tyranids themselves. Perhaps, even, Colossus was a standout of the ever-evolving Tyranid race, an artifact of Tyrannic evolution now lost to history.
Recorded Activity of Colossus
Hive Fleet Colossus started causing trouble for the Imperium in M39, when they launched an attack on Imperial-controlled worlds. After the initial encounter, Imperial forces were able to subdue and neutralize the Tyranid threat in half a century. However, at the last half of M41, it is believed that the remnants of Hive Fleet Colossus were able to re-organize and launch an attack on human worlds again. As of M42, Hive Fleet Colossus's activities are unknown, mostly due to the discovery of other multiple hive fleets throughout the galaxy overshadowing old Colossus.
|Tyranid Hive Fleets|
|Major Hive Fleets:||Hive Fleet Behemoth - Hive Fleet Kraken - Hive Fleet Leviathan|
|Minor Hive Fleets:||Hive Fleet Colossus - Hive Fleet Dagon - Hive Fleet Gorgon - Hive Fleet Hydra - Hive Fleet Jormungandr |
Hive Fleet Kronos - Hive Fleet Moloch - Hive Fleet Naga - Hive Fleet Ouroboris - Hive Fleet Tiamet