In the Black Sun, he encounters Hans Grosse guarding the machine that powers Deathshead's superweapon. In order to prepare the weapon, Deathshead and Grosse enter the Black Sun through a portal that Nazi scientists had excavated and reassembled. Alexandrov's treachery is rewarded only by an execution at the hand of Hans Grosse. Alexandrov was the real traitor all along. He boards the airship, where he discovers that Dr. Blazkowicz then finds out that a Nazi superweapon, powered by Black Sun energy, is about to be fired at the city from a zeppelin that has been hovering over the city since Blazkowicz first arrived in Isenstadt. Upon Blazkowicz's return to Isenstadt, Stefan Krieg informs him that he has killed his brother, Anton, thinking he was the mole and betrayed both Blazkowicz and Caroline. During a struggle, Caroline appears to be killed by Hans Grosse, Deathshead's henchman. He confronts Zetta's replacement, Obergruppenführer Wilhelm "Deathshead" Strasse, who is eager for revenge after Blazkowicz destroyed his Übersoldat-program in Return to Castle Wolfenstein. Blazkowicz helps the Kreisau Circle stage a rescue mission. Shortly after the move, Caroline Becker is captured and held in a nearby castle. The Black Market, the Kreisau Circle, and the Golden Dawn then move to a new location in downtown Isenstadt to escape retaliation for Zetta's death. Eventually, he manages to kill General Zetta, who turns out to be a monster when viewed through the Veil. As Blazkowicz completes more missions, he gains new weapons and new defensive and offensive powers for the Thule Medallion. In the Veil the player is able to run faster, jump higher and walk through doors which have the Black Sun symbol. With a crystal provided by Kovlov, Blazkowicz is able to enter the Veil, a barrier between the real world and a dimension known as the Black Sun.
The youth also shows Blazkowicz how to use the Thule Medallion. Kovlov introduces Blazkowicz to the Golden Dawn, a group of scholars who specialize in the occult, founded and led by Dr. He also finds an exact copy of the medallion that he found on the Nazi warship, which Kovlov calls the Thule Medallion. Becker sends Blazkowicz on a mission into a dig site, where he frees a young Russian named Sergei Kovlov. (He pays for upgrades with gold earned from missions or found scattered throughout the game.) He also meets the leader of the Kreisau Circle, a former schoolteacher named Caroline Becker and her lieutenant Erik Engel.
In Isenstadt, he meets the brothers Stefan and Anton Krieg, who run the Black Market where Blazkowicz can upgrade all of his weapons and powers. He then meets up with agents from the Kreisau Circle, a German resistance group dedicated to fighting the Nazis, and with them, makes it to Isenstadt. Blazkowicz is sent to Isenstadt, but his cover is blown by an unknown informant. The Nazis have begun digging for crystals, led by a general named Viktor Zetta.
During a meeting there, he learns that the medallion needs crystals called Nachtsonne, mined only in a city in Germany called Isenstadt, to make use of its full power. Hijacking a plane from the Tirpitz, he escapes and returns to the OSA headquarters. Discovered and captured, he unwittingly unleashes the power of the medallion, which kills all his foes for him. In an introduction sequence, special agent William "B.J." Blazkowicz steals a medallion from a general on the German battleship Tirpitz. Locations include the town's sewers, a tavern, a hospital, a farm, an underground mining facility, a church, the SS headquarters, a dig site and caverns, a cannery, a radio station, a paranormal base, a general's home, a castle, an airfield and a large zeppelin. As the game progresses, happenings in Isenstadt become stranger (military patrols are replaced by supernatural creatures, etc.). The story is set in the fictional town of Isenstadt during World War II, which the Nazis have enforced martial law in order to excavate rare Nachtsonne crystals necessary to access the "Black Sun" dimension.
This was the final game id Software oversaw as an independent developer, released two months after their acquisition by ZeniMax Media in June 2009. It was released in August 2009 for Microsoft Windows, PlayStation 3 and Xbox 360, to a lukewarm to positive reception by critics as well as poor commercial sales, selling a combined 100,000 copies within its first month. It serves as a sequel to the 2001 entry Return to Castle Wolfenstein, albeit loosely and uses an enhanced version of id Software's id Tech 4. Wolfenstein is a first-person shooter video game developed by Raven Software and published by Activision, part of the Wolfenstein video game series.