The Cycloid Emperor is a boss appearing in Duke Nukem 3D and it's long awaited sequel, Duke Nukem Forever.
Duke Nukem 3DThe Cycloid Emperor is the third and, prior to the Atomic Edition expansion pack, was the last boss in Duke Nukem 3D (Later on in Atomic Edition, was the third boss due to the Alien Queen being the final boss in the last episode of "The Birth"). It is the leader of the alien forces that are invading Earth. The Cycloid Emperor can fire rockets at Duke and fire a mental blast from it's mouth. After Duke defeats him, he kicks a field goal with his eyeball. In the 2016 20th Anniversary World Tour version, both the Cycloid Emperor and Alien Queen are no longer the final bosses as the Cycloid Incinerator (a revised, and possibly a hilariously weak edition of the Cycloid Emperor) takes the title in the Alien World Tour Episode.
Duke Nukem Forever
The Cycloid Emperor returns as the primary antagonist and final boss of Duke Nukem Forever, set twelve years after Duke Nukem 3D. In this game, he sports a new cybernetic black eye to replace the one Duke kicked from his skull in DN3D. He is also much taller and more mechanical in comparison to his appearance in the last game. He is first encountered in the beginning in a video game Duke is playing, which is a remake of the Stadium level of DN3D. While he is not seen until near the end the game, he is mentioned a few times by the President, who attempts several times to discuss terms of peace between the aliens and humans. When Duke destroys the Hoover Dam to close the portal to Earth the aliens are coming through, the Cycloid Emperor appears and kills the President, who had earlier ordered a nuclear strike to kill Duke. After Duke kills the Emperor once and for all by ripping out three cables on his arms and back, the Emperor's black eye falls out and Duke urinates in his eye socket, which he said he would do when the fight started.