During the 1100s, Barbarossa was once a Duke who later became King by King Conrad III during the latter's deathbed. He was later crowned Holy Roman Emperor by Pope Adrian IV in 1155. During his reign, he came to acquire a mystical blade that held mysterious powers with the use of a special type of energy later named Geistkraft, a power that could ultimately resurrect him when he would die. On June 10th, 1190, he unexpectedly drowned in the Saleph River and was buried at the church of St. Peter in Antioch. His blade was ultimately taken apart into several pieces and was scattered across the world in order to prevent his return.
Centuries later during World War II, a team of German miners discovered the hilt of Barbarossa's sword within a chamber in the salt mines of the mining town of Mittelburg within the Kyffhäuser Mountains. One of the miners, Klaus Fischer, contacted the Ahnenerbe to come to the town. Soon later, the Ahnenerbe arrived with the goal of collecting the hilt for Hitler's personal collection of artifacts. However, they soon discover the hilt is protected by a strange magentic force which prevents them from acquiring the hilt. With this drawback, they soon contact Nazi scientist Peter Straub and his team of scientists to come to the village, along with Gruppenführer Heinz Richter to try and help them recover the hilt. During this, they discover that the hilt is releasing a strange type of energy. The Nazis were able to begin to siphon this mysterious energy from the hilt until one day, a cable became overheated and snapped, striking a pair of guards and killing them instantly. However, the energy from the hilt proceeded to reanimate the two into zombies. While Straub was able to kill the first zombie, he nearly was killed by the second until reinforcements arrived and put down the zombie. With this, Straub soon came to realize the key to completing his task of creating a new type of army for Hitler.
As conflict between Straub and Richter began to expand over their new "Geistkraft" energy, Klaus saw this as an oppourtunity to sabotage Straub after discovering what Straub was intending to do. While doing this, Klaus uncovered a hidden story from the art of the chamber and soon learned of a secret organization dedicated to keeping the secrets of the sword hidden, as well as what the sword is fully capable of; resurrecting the Emperor. Knowing he has to stop Straub, he ultimately made contact with the Allies and his sister Marie, informing them of what has been going on at the town. He also began to hide things such as Richter's Tesla Gun and various others around the town for the Allies to find. Not long before the Allies could arrive, Straub caught Klaus attempting to sabotage his ultimate weapon, the Panzermörder, and ultimately fused him with it.
When an MFAA team lead by Marie arrived at the town, they manage to find the hilt of Barbarossa's sword in the tunnels and, after a series of trials, managed to break the seal around the hilt and recovered it. Before they could leave however, they encounter the Panzermörder and what has became of Klaus. After defeating the beast, they watch it destroy Ricther's zeppelin, killing the beast, Richter and Klaus in the process. However, with the use of the complete hilt, the team accidentally uses it to partially resurrect Klaus. Horrified of what has happened and what Marie has done, he ultimately commits suicide by incinerating himself within the Well Trap, but not before warning the team to keep fighting and that the Emperor must not return.