History of the Borderworld "Xen"

To most people, the idea of the existence of the Borderworld is on the lines of Science Fiction, however, after the Black Mesa Incident, its subsequent portal storms and the Seven Hour War; it is far more than general expectation and fact that the Borderworlds do indeed exist. As for how many there are, if all universes have them and if its just a unique feature to a select few universes is majorly unknown- but its existence proves clearly that multi-verse theory that was long believed as interesting myth is now undeniable fact.

Among the many worlds discovered by humanity, none is more infamous than Xen.

Xen is a Borderworld, a dimensional crossroads that exists between a few universes and realities. Rather than being a conventional planet, Xen is composed of vast floating landmasses suspended within an almost endless void. Its terrain is fragmented and often unstable, with entire ecosystems existing upon isolated islands separated by immense distances. Despite its hostile appearance, Xen supports a wide variety of alien flora and fauna, many of which would later appear on Earth following the Black Mesa Incident.

Long before Humanity discovered Xen, it had become the refuge to a powerful being known as the Nihilanth. Having fled from the Combine, the Nihilanth established itself within the Borderworld and gradually transformed Xen into the center of a growing empire. Numerous species became trapped within its domain, either arriving naturally through dimensional displacement or being forcibly relocated by the Nihilanth's forces.

Amongst these species were the Vortigaunts, who would later become one of the most important races in modern human history. Through a combination of advanced technology and biological manipulation, the Nihilanth enslaved much of the Vortigaunt population and used them as laborer's, soldiers and servants throughout Xen. Other creatures familiar to Humanity; including Headcrabs, Houndeyes, Bullsquids and countless other lifeforms also came to inhabit the Borderworld during this period.

Humanity's first direct contact with Xen occurred during the Black Mesa Incident. The Resonance Cascade weakened the barriers separating Earth and the Borderworld, allowing Xenian organisms to cross into human-controlled territory leading to an Xenian invasion within the borders of the United States. In response, Black Mesa's Lambda facility was later able to open their own gateway into Xen, culminating in the death of the Nihilanth at the hands of an individual later identified as Gordon Freeman.

The consequences of the Nihilanth's death were immediate. Its empire collapsed, its armies fragmented, and the Vortigaunts were freed from centuries of enslavement. For a brief period, Xen existed without a dominant power for the first time in generations. Despite this newfound freedom, the consequences of the Resonance Cascade continued to reshape both worlds. Throughout the four-year Portal Storm Crisis, countless Xenian lifeforms, plant species, and even entire fragments of Xen's ecosystems were deposited upon Earth as unstable dimensional breaches continued to link the two worlds together.

This period of freedom proved short-lived.

Following the arrival of the Combine, Xen became another target of their expansion. The Borderworld's strategic position between dimensions made it far too valuable to ignore. Over time, Combine forces established control over large portions of Xen, forcing many surviving inhabitants into hiding while others fled to worlds beyond Combine reach.

Today, Xen remains one of the least understood locations known to humanity. Much of its vast expanse remains unexplored, its ecosystems poorly documented, and its current political landscape largely unknown. What is known is that Xen continues to serve as a gateway between worlds; and as a reminder of the events that first brought humanity into contact with forces far beyond its understanding.