The Nihilanth floated enchained, enmeshed in agonies. The light of colors without name bound it implacably. "You are nothing," said the voice that echoed in its mind. "And yet you hear me, you feel everything, and in your pain you cast off the very stuff that holds the universe together."

Horrible as the Nihilanth may have seemed, there was another thing more awful still which tormented it.

The Vortigaunts were not enslaved, except in the broadest sense. They did their duty out of devotion, and whatever befell the Nihilanth they accepted gratefully. It had been so always, in their collective memory; but the Nihilanth could still dimly recall a time when it had not been so, a distant age when it had not yet gathered so many entities around itself and made them necessary to its existence, forming a complex colonial organism which was sentient and malevolent in all of its parts.

There are numerous stories of humanity on the edge of reaching the stars—a small-minded and predatory race, more dangerous to others than even to itself, on the verge of extending their reach throughout infinity. Usually the technology that they are about to discover is that which makes space flight possible, faster than light travel. In Half-Life, the technology is teleportation.

Initially.

Teleportation has been mastered by a chain of superintelligent (compared to us) aliens. Mainly, they use it to exploit and enslave the races they encounter; their exploitation may be open or it may be extremely covert, involving political manipulation of the worlds they control. It all depends on what they want out of the species they intend to dominate.

The civilizations which are potentially the most dangerous—and also the most useful—to them are those which have independently arrived at the creation of a teleport technology which could surpass their own...for as in all things, even advanced alien superscience is bound to become obsolete, and the drive for a more powerful technology is unending.

Earth is at exactly this point. We made a few strong experimental forays into the science of teleportation, began to discover the practical underpinnings of the art, and then succeeded against our wildest dreams—stumbling into a weird dimension whose properties defied our understanding of natural law. Nor were we alone in this realm, which we named Xen—for that which is forever alien and inexplicable.

Xen proved to be a meeting place, a point where universes collided and hung in endless freefall, the elements of countless worlds intermingled. No sooner had we begun to explore Xen—with particular attention to its wealth of natural resources with unknown properties—than we found ourselves the object of unwanted inspection. Members of the survey team were collected in a cold and systematic manner, much as we gathered living specimens of alien wildlife. Realizing our precarious situation, we shut the portal completely, stranding the last members of the survey team and forcing them to survive alone in Xen.

But shutting our gate was not enough, for now the predators of Xen had traced our signal—found our location. And come looking for us.

The only hope seemed to be to find their portal and close that down from Xen itself; but we had lost contact with the survey team, and there was no one willing to cross over until Gordon Freeman reached the lambda portal. Eventually he reached the portal and killed the Nihilanth, which held the portal in existence by a concentrated effort of thought. But there was a deeper mystery awaiting him on his return to earth.

We had been pointed to Xen, all our efforts aimed there. Rather than a random fumbling through the white noise of possible cosmos which the teleport might have reached, we had settled almost immediately on Xen. The cause of this was a certain element, found in Xen, which had been made part of the portal’s tuning mechanism. It was introduced into the portal research with the pedigree of a man-made compound, something created in a separate secret research facility, but actually it was imported to Earth by a devious route, involving several of the aforementioned superintelligent alien races. By steering us to Xen, they immediately forced a confrontation with a troublesome race which would either annihilate us or force us to show our mettle. If the former were the case, then they were rid of a pest. If the latter, then they would further shroud their presence in secrecy and work their manipulations deeper into the fabric of our society, in hopes of harnessing us from within.

The G-Man is [REDACTED].

Teleportation is only the first of many new empowerments for humanity. Greater surprises await us as we begin to plumb the depths of the universe, finding in Xen the gateways to all the other worlds. For Xen is the waystation, essential to all travel that takes us out of this universe and into the next. Whoever controls Xen, controls all the worlds. And the battle for Xen is just beginning...It will rage on Earth, it will rage on Xen, it will consume entire realities before it ends.

Beware! Yours may be one of them.