Hive Fleet Tiamet

Hive Fleet Tiamet is a small Tyranid Hive Fleet first encountered in M35, considerably sooner than the first major Hive Fleet, Behemoth.

Discovery of Tiamet

Hive Fleet Tiamet was first encountered around the Tiamet system, on the eastern side of Ultima Segmentum. Considering this region is quite unremarkable for any of the major powers of the galaxy beforehand, the Imperium made first contact with it through a small Explorator Fleet, technically making this the Imperium's first contact with a Tyranid Hive Fleet. They didn't consider the presence of the tyranids in the worlds around Tiamet something threatening, believing they were just the natural fauna of a Death World. Because the Imperium had other things to worry about, and because the area had no real value, it was left undisturbed (they did throw a symbolic bombardment of the place once, though, to no real effect).

It wouldn't be until a fleet of Eldar explorers when someone recognized the Tyranids for what they were. However, they never reported it: the Shadow in the Warp had grown so powerful in the region that they became comatose.

Behaviour of Tiamet

Regular tyranids follow a nomadic lifestyle, travelling though the galaxy and devouring whatever planet or biomass source they can find, usually following the psychic beacons activated by the multiple genestealer cults spread throughout the galaxy, leaving wherever they go bereft of life. Hive Fleet Tiamet follows a radically different lifestyle. For some reason, these Tyranids inhabit the Tiamet system and its surrounding planets exclusively and don't fully strip them of biomass. And they guard the place very zealously, too. Every time a merchant or an exploration fleet gets close to the system, it gets immediately swarmed by the nids, who drag it off to their main stronghold on the world of Ziaphora. The genestealer cults serving them act similarly, with their leaders bringing the cult to a supposed "paradise planet" in the system.

Eventually, so many ships were lost that a Kill Team was sent to explore the area to figure out what had been going on over there.

Ziaphoria's Tower

When the Kill Team arrived to the place, they discovered a massive organic towering structure (as in, the size of a continent) on the jungle forest of Ziaphoria, the largest planet in the system. What that thing does, nobody knows, but it's been speculated that is a massive psykic beacon to attract other Hive Fleets. The device is psychic alright, generating such a powerful Shadow in the Warp that when the first Eldar appeared there their heads almost exploded from the shock of it. The Kill Team that visited the place was joined by a Librarian, who actually had his head explode from the strain.

Whatever this thing is, everyone in the galaxy agrees it's no good. The Ordo Xenos is extremely interested in taking this thing down, and has contacted excommunicated Inquisitor Kryptman to find out what it is and how to take it down.

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