This was the Warp Sea, also known as the Immaterium, the Sea of Souls, the Empyrean.
As the opposite of the material universe, the emotions of endless life from countless worlds gathered here, forming the indescribable, ever-shifting tides of the Warp.
The Warp was exceedingly dangerous. Whether it was the impossibly tangled relationship between time and space, or the invisible Warp disasters that could devour all existence, both were nightmares to every visitor.
Yet it was precisely through the Warp's disorder that humanity could travel faster than light and sustain a galaxy-spanning human empire.
The Astronomican created by the Emperor gave all humans entering the Warp a coordinate to observe. With its light illuminating the path ahead and guiding their course, humanity could travel through the Warp efficiently.
And not long ago—at least, not long ago for travelers within the Warp—the light of Terra's Astronomican had gone out.
An unstoppable Warp storm had cut off the Astronomican's radiance, plunging the humans within the Warp into immediate peril.
The Sea of Souls seemed to have flown into a rage. Under the storm's lash, everything became even more unpredictable, yet in such a terrifying environment, a Zeta-class messenger vessel named the Crescent Moon still stubbornly drifted with the currents.
Even compared to human warships, it was a very small vessel. Its hold carried only a squad of Space Wolves, along with a handful of necessary mortal attendants and Mechanicum priests responsible for maintaining the engines.
Fafnir Blood-Bond recalled the oath he had sworn before the primarch of the great Sixth Legion, Leman Russ, the Wolf King. These Space Wolves had been tasked by the Sigillite, Malcador, to each lead a squad and watch over those primarchs whose loyalties remained uncertain.
After the Burning of Prospero, the Sixth Legion had indeed dealt the