We have seen a lot of a rumors and leaks for this codex, so while this may not be all new, it gives a great look at the new Tyranid codex and what that will bring to its hordes.
via Warhammer Community
The Tyranids are horrifyingly diverse, and now, you’ll be able to build your army as dedicated to one of seven hive fleets (or their splinters). Each of these army-wide rules affects every unit in your Tyranids collection, from Rippers to Tyrannofexes, and each is powerful, distinct, and flexible.
Tunnel Networks may make your Tyranids army a little slower, but being able to claim a bonus cover-save anywhere on the board is well worthwhile. From Genestealers with extended carapaces claiming a 3+ save, to Exocrines with a 2+, this is the go-to Hive Fleet Adaptation for defensive players.
Swarming Instincts allows Tyranids players to take advantage of the cheap infantry available to their army. Outnumbering the foe is simple with units like Hormagaunts and Gargoyles, and re-rolls to hit help make up for the fairly average Weapon Skill on most smaller Tyranids units.
Hive Fleet Kronos turns the Tyranids into a powerful shooting army, bolstering the army’s already capable ranged units. From a unit of Termagants dousing the foe in devourer shots, to an Exocrine unleashing a super-hot hail of plasma, going with Kronos allows you to focus on the potent bio-firepower of the Tyranids.
As you can see, the new Hive Fleet Adaptations allow for you to customise your Tyranids army to suit nearly any play style you see fit. It doesn’t stop there, either – come back tomorrow, when we’ll be looking at the manifold ways in which you can build Tyranids HQs in the upcoming codex, from a new option, to Bio-artefacts, to a warlord trait that’ll devastate enemy Psykers…