Tyranid FTL

• Devastation of Baal:

"As you watch you will see it consume world after world, although in reality these planet deaths were months or years apart. Its progress is slow by our standards. By some mechanism the tyranids are able to violate natural law and exceed the speed of light somewhat, but as far as we know the fleets cannot traverse the warp. Over the last few decades this has offered us a small strategic advantage, as we have been able to respond more quickly than it has. Nevertheless, I cannot claim any sort of victory"

• Devastation of Baal:

"‘My lords!’ The Servile of the Watch spoke up. ‘I have hundreds of incoming contacts.’ Tocsins sounded. On the tactical displays of the command deck a swarm of red lights made itself known. ‘Revision. There are thousands,’ said the Servile of the Watch. ‘Tens of thousands.’ Erwin leaned forward. Nothing was visible in the oculus, only the vileness of the Scar and the occasional glint of a comet turning about its axis. ‘How fast?’ asked Erwin. ‘Super-light speed, my lord,’ said the servile. ‘My augurs show massive gravitic disturbances at several distinct points.’ ‘Adjust orientation towards the nearest,’ said Erwin. ‘Adjusting,’ said the Servile of the Helm. As the servile spoke these words, Erwin witnessed a rippling of the view forward, the bending of light due to manipulation of gravity. Something was hiding behind the distortion. ‘There they are,’ said Erwin. ‘There they are!’ ‘All vessels of the Angels Excelsis. Prepare for battle.’ Erwin snorted. Follordark had never been one to make grandiose speeches. The rippling cut out. For a moment the oculus was full of streaks. These compressed themselves into the solid shapes of tyranid bio-ships that shone wetly with deep space ice. Small, teardrop-shaped vessels bristling with sensor spines were breaking from the fore, heading back towards the shelter of the vessels coming behind."

• Tyranid 5th ed codex:

"Tyranid Hive Fleets do not travel through Warpspace. Nonetheless. the Hive Fleets' incredible rate of advance belies the supposition that they are bereft of a swift mode of travel. Whilst it is true that the Tyranids are constrained by sublight speeds whilst within the borders of a planetary system. they are capable of far greater velocity when traversing interstellar space That they can do so is thanks to an almost innocuous vessel classified by the lmperium as a Narvhal.

Unlike most Tyranid vessels. a Narvhal is almost completely defenseless. with little in the way of bio-weaponry and a comparatively thin protective carapace. A cluster of monofilament spines on the Narvhal's bow enable it to interpret a wide range of sensory input. including an unbelievably broad spectrum of gravimetric signals. Using these senses. the Narvhal can detect planetary systems at incredible distances. it can then somehow harness that systems own gravity. creating a compressed-space transit corridor through which the Narvhal, and nearby vessels, can cover vast distances. This method cannot be employed near to strong gravitational forces, as they drown out the more subtle traces that the Narvhal uses to navigate. As a result, a Tyranid fleet must rely on more conventional propulsion in the final approach, in some cases slowing their arrival by years, or even decades. Whilst this combined propulsion method is slower than Warp travel, it is infinitely more reliable. allowing the Tyranids to conduct their implacable encroachment across the galaxy.

The Narvhal's manipulation of a star system's underlying forces is not always without side effects. A prey planet will sometimes be subjected to earthquakes, solar flares, tidal waves and other natural disasters in the time between the Narvhal casting its gravitic snare and the Hive Fleet actually arriving. This only benefits the Tyranids‘ efforts,guaranteeing as it does that the defenders of the target world will still be wrestling with planetary disaster when the swarm arrives in orbit."