Well, I have 4 army lists to represent what I believe the 4 stages of a Tyranid Invasion might look like:
1) Invasion - Loki
2) Scout (aka Lost Blue Skies) - Hel
3) Harvest (My default) - Jormungand
4) Razing (Formally Kerberos) - Fenrir
Wow, this is one old post, Peroyasha, but I only saw it now. It is curious because my fleet is set up in a similar manner; however, I call the whole fleet fenrir and use "Loki," "Jormugand," and "Hel" to refer to different TMCS in it.
Hive Fleet Fenrir
Hive Fleet Fenrir got its name from the similarity of its circumstances to the myth of Fenrir in old Norse Mythology. Fenrir was chained to a mountain and was destined to stay there until the coming of Ragnarok, the war of the Gods, when Fenrir would break free of his bonds and kill Odin, king of the Norse gods.
My fleet was created from the remains of a large spawning ship (from Hive Fleet Behemoth) that crashed on a jungle world. When the ship crashed on the planet, it bored its way into the surface, getting closer to the warm core of the planet (stolen from SNES game "Chrono Trigger"). Here it slumbered while the Tyranid constructs on board started leaking onto the surface of the planet and slowly transforming it into a hybrid Tyranid-jungle ecosystem. The ship remained grounded on the world until it could repair itself.
Once it was again capable of space travel, instead of lifting off, it began to convert the planet into one giant hive ship. It consumed the very bedrock and magma at the planet's core to feed its evolution. In the place of the bedrock, it grew new organs for creating tyranid organisms, and on the surface it grew new organs that would allow it to move the very planet through space (stolen from Mainframe TV show "Shadow Raiders/War Planets"). In this way, the ship used the planet's crust as a durable shell to protect it, while still preserving a mutated version of the planet's native ecosystem on the surface. This ship at the core of Hive Fleet Fenrir was the first recorded instance of a Tyranid planet ship.
The Harbinger of Ragnorok
Once the Tyranid planet breaks free of its restraints and begins to move, it will signal the coming of Ragnarok, the Tyranid invasion that will bring the hivefleets within striking distance of Terra and the Emperor.
Another unique feature of the fleet is the way in which it gathered new genetic material to rebuild itself after the crash. The original ship from Hive Fleet Behemoth carried a strain of lictor that was once imployed by the Hive Fleets for gathering genetic material ahead of a Tyranid invasion. This stain of Lictor was labeled as "genetic scout" by the Imperium, and it allowed swarms to adapt to the organisms on a given planet long before the actual fleet reached that planet.
One such lictor survived the ship's crash on he jungle world. By using the weakened synapse pulses of the crashed ship to attract a nearby genestealer cult to the jungle world, the Lictor was able to secure transport off the planet to seek new genetic material for the weakened hive ship to assimilate.
The cult worshiped the lictor like a god. Using tyranid pheremones and some kind of latent synapse ability, the lictor was able to communicate with the cult's magus and inform them of the lictor's role in gathering genetic material to rebuild the fallen hive ship and the broods it housed. The cult named the lictor Loki and ferried it across the imperium in their stolen starships, heping it to collect the genetic material needed by the swarm.
Naming Convention for TMCs
The naming system used for the TMC characters in the swarm and the broods spawned from them references Norse Mythology as well and is tied up int he idea of this genetic scout lictor being the progenitor of the swarm's current incarnation. Each of the TMC creatures has been named after a different Norse deity by the Genestealer Cult that worships Hive Fleet Fenrir.
Loki is the Uber-Lictor (Midnight Drake, Malin's Bane, Polocks Daemon, yet to be modeled) who was smart enough to nurse my fleet back to strength by hunting down new strains for incorporation.
Jormugand is my Red Terror who was the first child of Loki (Loki steals the DNA to create Jormugand in the Malin's Bane
story on hivefleetmoloch.com) and was the basis for the raveners in my hive fleet.
Hel is my Old One Eye who was the second child of Loki (DNA stolen in some other event that has yet to be documented) and the basis of the large, regenerating Fexes in my swarm.
Fenrir has yet to be born (or modeled for that matter because I keep changing my mind on him) but will be modeled as a flying hive tyrant and will be the basis for the gargoyles and winged warriors in my swarm. When Loki births Fenrir, it will be the symbol that the swarm is complete and can move against Odin (the emperor on Terra).
So, yeah, I've given it some thought.