Heinrich I

 Heinrich I is the main antagonist of Return to Castle Wolfenstein. He is an ancient German warlord who long ago set out to conquer Medieval Europe, only to be defeated by a monk named Simon the Wanderer. The entire plot of the game revolves around Operation: Resurrection, a plan by Heinrich Himmler to bring him back from the dead and use him to help the Third Reich conquer the world.

Role in Return to Castle Wolfenstein
Heinrich first appears in the intro, where he is banished by Simon the Wanderer in 943 A.D, apparently bringing an end to his reign of terror. However, the spot where he was banished is unearthed 1000 years later by a Nazi excavation team, somewhere outside of Castle Wolfenstein. This leads Himmler's SS Paranormal devision members Helga von Bulow, Wilhelm "Deathshead" Strasse, and High Priestess Marianna Blavatsky to plan his return through a mix of technology and the occult, and it is up to OSS Agent BJ Blazkowicz to stop the resurrection.

Return, Battle with Blazkowicz and death
Heinrich does not appear again until the end of the game, where he is brought back to life by Marianna Blavatsky, whom he then "rewards" by turning her into an undead minion.

Heinrich I is the final boss of Return to Castle Wolfenstein, and must be fought to win the game. In the end, he is destroyed by Agent Blazkowicz and Operation: Resurrection is ruined.