Gordon arrives within the lair of Nihilanth, the supreme leader of the forces of Xen who Gordon's been hearing in his head throughout his exploration of the alien world. In addition, it's Nihilanth who's keeping the rift between its world and Earth open for its armies to continue invading the planet.
Gordon faces off against Nihilanth, who's primary means of combating the human is firing a barrage of electric orbs, or by throwing teleporter orbs that could send Gordon off to small trap rooms that he will have to escape from to return to the Nihilanth's room. Meanwhile for Gordon, he has to destroy three large Xen crystals in the lair that restore Nihilanth's power whenever its drained or taken significant damage. Once the crystals are destroyed, damaging Nihilanth will eventually lead to its head opening up, and leaves its brain exposed for Gordon to finally land the killing blow. As Nihilanth suffers a prolonged agonizing death and is on the verge of exploding, Gordon is then suddenly teleported out of the lair.
This Chapter contains examples of:
- Final Boss: Gordon faces off against the supreme leader of Xen known as Nihilanth.
- Sidetrack Bonus: It's possible to beat Nihilanth without ever being sent off to the trap rooms that the boss sends you off to with its teleporter orbs. However, these trap rooms are still quite useful as they're filled with supplies.
