Gnosticenes. These old guys are the ones you're supposed to save in Keen 4. The Shikadi kidnapped them and put them in the Shadowlands. They are the guardians of the oracle, and the only ones that can activate it. They are also immortal.
Creative Director. He is one of the most well known makers of Keen and the supposed best hope for The Universe is Toast series. After working at numerous other companies, he now created a company called Monkeystone with John Romero, however he now works at Midway.
Commander Keen's arch-nemesis. Mortimer is usually behind all the schemes to destroy the universe or take things over. He has been known by some species as the the Gannalech or Grand Intellect.