Keen 5 Story
Commander Keen 5: The Armageddon Machine starts right after Keen 4 ends. Having previously freed the Council Members from their exile in the Shadowlands and having had them activate the Oracle (see Keen 4 Story), Keen learned that the Shikadi are in the Korath system and are planning to destroy the Milky Way with their Armageddon Machine, the Omegamatic.
Keen rapidly heads to Korath III, where the Omegamatic is being constructed in orbit around the planet. Once there, he sneaks aboard the lower floors by docking with a ventilation duct near the main exhaust.
Once onboard, Keen goes nuts, shooting all sorts of robots, defenses, and creatures, including the Shikadi. His aim is first to make it past the lower floors to the main deck, then to destroy each of the four machines protecting the main elevator shaft. (Each of which is protected by a defense tunnel.) This grants access to the second elevator, allowing Keen to use it to travel to the upper deck where he may then attack the core of the Omegamatic, the Quantum Explosion Dynamo.
At the end of this episode, a suggestive announcement about The Universe Is Toast was made, but id Software moved on to bigger projects, such as Wolfenstein 3D, Doom and Quake, and so the promise was never fulfilled.