You step out from between dark towers into the glowing core of the Nihilanth's power. At first all you notice is the Nihilanth itself, a supreme and supremely tortured intelligence, suspended in space above a bottomless abyss. It begins to drop toward you, as if you were worth noticing; and you shrink back in fear, for you are weak and nearly defenseless after your ordeal in the Gonarch's den. As it descends, an alien pulse or heartbeat begins to toll—slowly and softly at first, but gathering intensity. But then you see that it is coming not for you, but for something which is emerging from the open portal down below.

Two Xen Masters, their bulbous heads gaping in the presence of their living god, rise up with a struggling morsel trapped between them. It is a suited figure like yourself—a scientist, probably, one of the survivors of the survey team. At any rate, a human being. They drift up from the portal and take advantage of the lowered gravity at the core to sling their prize straight up into the maw of the Nihilanth, while sinking back themselves into the portal. A moment later, the awesome sight repeats itself. They are feeding the thing a steady diet of people.

You want only to get away...to remove yourself from any possibility of its noticing you. You discover an opening near at hand, a place perhaps where you can hide. But even as you enter, you can hear the electric crackling of the Vortigaunts. This place cannot possibly be safe—and yet...there is nowhere else to go.

Within, the Vortigaunts are busy. Too busy, in fact, to take notice of your presence. The air is charged with their power, and yet the trails of energy are aimed not at you but at the powerful machines that crowd your path. The creatures work in unison, tapping power from immense reservoirs and feeding it into huge cathodes, segregated into a few separate tasks in the first few rooms you explore. You move among them, avoiding the lighting blasts, but otherwise unhindered. But eventually you find a human prize, another scientist in an HEV suit, imprisoned in some sort of device which is drawing out his soul. You take his weapon and he begs you to kill him—and in fact, there is no other way to progress.

Once provoked, the Overmind lets out an alarm and raises its arms. Lightning flickers from its fingertips, sweeping the ground around you. A tide of snarks comes seething from every surface—spawning from teleports, appearing between crannies in the stone. They threaten to engulf you. You can fight them with the hivehand, and by leaping across gaps in the rock and using the effects of lowered gravity to dodge them, causing them to fall into the void. The Overmind fires jolts of psionic lightning at you, which has the advantage of crisping many snarks.

Once provoked, the Overmind lets out an alarm and raises its arms. Lightning flickers from its fingertips, sweeping the ground around you. A tide of snarks comes seething from every surface—spawning from teleports, appearing between crannies in the stone. They threaten to engulf you. You can fight them with the hivehand, and by leaping across gaps in the rock and using the effects of lowered gravity to dodge them, causing them to fall into the void. The Overmind fires jolts of psionic lightning at you, which has the advantage of crisping many snarks.

When you have mostly beaten the snarks and inflicted sufficient damage on the Overmind, it will begin to retreat, rising through the iris into the darkness above. As part of its retreat, it blows out the floor, and chunks of rock begin to rise in the Overmind's wake. [DESTRUCTION OF ENVIRONMENT; RELATIVE MOTION/PARALLAX EFFECTS; MOVING TRAINS] You must keep your footing on the fragments, for they will carry you to the dark transition above. You are carried through a transition into a .bsp stacked directly above the first.

Zone 2: Controllers, Conveyors and Homing Missiles

Floating up into the second level, you find the Overmind awaiting you. (The region below is now completely dark, except for the orange beam extending upward.) It is accompanied by Controllers, who immediately come after you. [SQUAD/FLOCKING AI] The orange beam still streams up from the level below, and the violet beam extends from its crown straight up through another iris in the ceiling of this area. The surrounding rocks are less frequent here—it is much easier to plunge into the sky. Navigation in this area is accomplished via some sort of organic conveyor belt equivalent...a surrounding webwork of living goo-strands whose cilia scull you along the "walls" and across the space while the Overmind attempts to eradicate you. [CONVEYOR BELTS]

The pulsing heartbeat is even louder here, and it is now mixed (very occasionally) with a chilling alien whisper which sounds all too much like "Gordon Freeman" being uttered by an orifice unaccustomed to human speech. Possibly a telepathic threat—at any rate, evidence of recognition. The Overmind knows you. You've managed to become something important to it. [AUDIO EFFECTS]

The Overmind now starts drawing on its secondary attack–a "homing salvo" attack. It periodically (and frequently) fires off a cloud of silver spheres (directly related to the Controllers' spheres) which scatter about in random directions then converge on your last location, exploding with tremendous force. You must stay on the move constantly to avoid being caught by the spheres. [AMAZING MONSTER BEHAVIOR]

You can do only limited damage to the Overmind from your awkward position. Every time you try to get the advantage of height, it rises toward the ceiling, giving the impression that its crown is fairly vulnerable. Whenever you kill the existing Controllers, the Overmind will send jolts of lightning out to portals located in the level, and summon in reinforcements; it will do this until, injuring the Overmind directly, you cause it to flee. When you have injured it sufficiently, and taken care of the Controllers (hopefully by luring them into the path of the Overmind's homing spheres), the Overmind will retreat once more through the open ceiling. The area darkens. You follow through a transition into the third and final of the stacked levels.

Zone 3: The Portal

In the third level, you see that the violet beam connected to the Overmind's crown is connected to a large portal mounted in a floating web directly overhead. The portal is open at the bottom (where you cannot reach) and guarded by some kind of mesh or protective cage on the upper portion, so you cannot jump in. Showers of lightning, energy beams, sizzle down from the portal, giving juice to the Overmind. [BEAM EFFECTS] Up here it is almost alone. The two of you hang in a darkened sky. There are enough chunks of circling and bobbing rock to allow you to make your way directly overhead and into the webwork, where you at last escape the lightning attacks and find good footing. But the gravity is lowest here, and you must be careful not to leap incautiously, or you will find yourself falling straight toward the Overmind and its sparking crown of lethal energy.

At the third level, the Overmind could introduce yet a third attack in combination with its lightning and salvo attacks. This is still unspecified. [MORE MONSTER BEHAVIOR]

Now that you are directly above the Overmind, you are finally at an advantage. It cannot fire lightning up at you because the portal is in the way. It is fairly easy to dodge the homing missiles up here. The pulse is at a high pitch, but the wailing telepathic echo of your name is almost pitiful. [AUDIO]

You can fire directly down into the core of the Overmind's brain. You find the body of a fellow scientist trapped in the webwork, with tripmines and grenades, and by lobbing several of these into the Overmind's sensitive region, you eventually wear the beast down to nothing—it implodes violently, splattering the rocks and portal-web with alien gore. [DECAL EFFECTS] Lightning and sparks are spawned to fill the area at the instant of death, and when they subside we see the orange portal beam from below growing stronger and stronger. In the absence of the Overmind, the orange beam has arced straight into the heart of the portal, and the portal is starting to go critical. [BEAM EFFECTS]

The cage surrounding the portal shatters [DESTRUCTION OF WORLD OBJECTS], opening the way for you to jump in. A high-pitched electronic shriek signals that the portal is overloaded and about to undergo a cosmic meltdown. The Overmind's pulse has been replaced by a scream of pure energy rising to a killing pitch. An explosive power starts climbing the orange beam, shooting up the shaft from the levels below. You see a blazing pulse of death surging toward you from the hollow pit. Before it reaches the portal, you must leap in. If you remain behind, the explosion kills you. [EXPLOSION EFFECTS]

Then we switch to a third person camera, showing Gordon framed within a circular portal: a tiny speck or silhouette tumbling against a background of immense explosions. Everything goes white. When it fades, we are back on Earth.... [SCRIPTED SEQUENCE/NARRATIVE]

NOTES:

Apart from its attacks (lighting and homing salvo), the Overmind's behavior is fairly simple. It needs to rotate to follow your location, and it needs to rise and fall within a restricted cylindrical space.

It would be great if the Overmind were not immediately visible, but partially shrouded in darkness, revealed by the flashes of its lightning attack. At the very least, when you commence battling it in the lowest level, it might show you only its lowest portions, and you won't get sight of the entire creature until you climb above it in the uppermost level—where the play of portal lightning reveals the entire anatomy of the thing.

Health should be resupplied to the player in the form of floating localized pools of healing light...energy effects that are common and random in Xen, and which you will have learned to use by now. In the upper areas, they will be located in mid-air, so that in order to heal yourself you will have to make some precarious jumps through the middle of a healing light. Weapons and ammunition should be refueled with the bodies of your peers, which can be located in crevices.