|“||It’s William’s prison... The prison your father was commissioned to build.||”|
William's Prison is a dungeon excavated under a secluded fortress belonging to the Vampire Elder Viktor, with the intended purpose of keeping William Corvinus captive. The castle is located in a mountainous valley high up in the Carpathian Mountains, and is almost completely surrounded by a large river.
The dungeon is accessible via a river entrance. A sarcophagus-like cell, specially designed for William, is located in a chamber which can only be accessed through a trick wall, and both of which can only be opened by a special key. Bridges and stairs are located throughout the dungeon, giving the location a Gothic feel. Doors throughout the dungeon can only be opened through the use of a specially designed key.
After the Vampire Elder Viktor captured and took custody of the first Werewolf, William Corvinus, he looked for a way to keep William imprisoned, so that he could not spread his bloodline any further. Around two hundred years later, a talented master stonemason and metalsmith came to Viktor's attention. Viktor approached and commissioned him as an architect to design, excavate and build a new dungeon beneath a fortress of Viktor's, secluded up high in the Carpathian Mountains. The builder was also asked to strike two unique keys to William's cell, which would be given to Viktor upon completion of the prison. Exactly where and how Viktor had kept William locked up before this is never touched upon.
During construction of the prison, the excavation site served as a playground of sorts for the stonemason's two daughters, Cecilia and Selene. It is unknown when work on the dungeon began, or how long it took, but the stonemason's youngest daughter, Selene, was around 6-7 years old when the site reached completion.
After the dungeon was completed, and William placed inside his permanent cell, the dungeon would also see the imprisonment and torture of other prisoners before being abandoned. Over the centuries, the fortress fell into ruins, and the rising water levels of the river flooded the lower levels of the dungeon via the river entrance. When Selene revisits the prison six centuries later, she takes note of the weapons, torture implements, and even skeletal remains of a prisoner still held up by shackles. She mentally compares the dungeon to the chambers used by Vampires for the torture and interrogation of Lycans.
In the year 1402, Viktor's daughter, Sonja, was executed for having an affair with a Lycan servant named Lucian. Lucian was able to steal Sonja's pendant, which contained half of the key to William's prison. Worried that Lucian would find and release the uncontrollable William, Viktor began to track down and kill all of the men who had helped build the location. Viktor was so obsessively afraid of Marcus finding out where his brother was hidden that he even lied to the men who helped him in executing the families of the dungeon's builders, telling them he was merely in need of blood. Viktor tracked down the head builder and slaughtered his family with the aid of Soren and Kraven, before stumbling on to the builder's 19 year old daughter, Selene. Despite that her memories of the prison would remain a constant threat for the centuries to come, Viktor turned the girl due to her startling resemblance to his deceased daughter.
By the early 21st century, the only people who know of the existence of William's prison are Viktor, Andreas Tanis and possibly the third Vampire Elder, Amelia. Marcus begins to suspect that Viktor killed Selene's family to keep the location of William a secret when he drinks Kraven's blood and sees his memories of the night Viktor slaughtered Selene's family. Marcus notes that Viktor was not totally honest with him about why he turned Selene, and he starts tracking Selene and her Hybrid lover, Michael Corvin. Initially, Selene and Michael are confused as to what Marcus wants, so they approach exiled Coven Historian Andreas Tanis for answers. Tanis tells Selene why Viktor killed her family, a truth she had been ignorant to until the previous night. He then reveals that Selene and Michael are currently in possession of half of the key to William's cell, and that they must stop Marcus from taking it. As Selene studies the key, she begins to remember playing in the prison as a child.
The pair travel to the Sancta Helena, where they meet Alexander Corvinus, the eldest of the Immortals and the father of Marcus and William. After Alexander refuses to help Selene and Michael to stop Marcus, Selene is trapped by Marcus, who uses her blood memories to find his brother's location.
To stop Marcus from freeing the dangerous Werewolf, Selene travels to the prison with the Cleaners, a group of men who work for Alexander Corvinus. There, they arrive too late, and William is set loose by his brother. Selene fights Marcus, and is eventually able to lock him behind one of the prison's doors. During that time, the Cleaners are killed by William, causing their bodies to turn into Werewolves. Selene kills the newly formed Werewolves with the help of Michael, who then fights William.
Marcus breaks free of the door trapping him and attacks Selene. During their fight, Michael kills William by ripping his head in two. Marcus is temporarily distracted by the death of his twin, which gives Selene an advantage over him. Enraged, Marcus stabs Selene through the chest with his wing talon. Selene then tears the talon from Marcus's body and stabs him through the jaw with it, before pushing him into the still-whirling blades of a crashed helicopter.
With Marcus and William dead, Selene and Michael leave the prison behind, littered with the corpses of the Cleaners and the Corvinus twins.
William's Prison is unlocked by a pair of unique keys, which when brought together and combined, become the one key that alone opens both the trick wall that hides the secret chamber that houses William's cell and the cell itself. Together, they play a crucial plot device in the Underworld franchise.
The commissioning of Selene's father to build the fortress also included the striking of a unique key, which could be divided into two and kept separated. The keys were cast from solid bronze. Both keys featured a mechanism, which when triggered, would release four teeth-like latches from the edges of the circular keys. The mechanism on the smaller key was triggered by depressing the green stone in the center. The mechanism in the larger key, however, could only be triggered by inserting the smaller key, with the latches out, into the larger key's centre. While the films show that the complete whole key is required to activate the trick wall and William's cell, the novelization describes that only the pendant piece was required to open the wall, and the whole key was needed to open William's cell.
After the dungeon was completed, and William placed inside his permanent cell, Viktor divided the keys between himself and his daughter, Sonja. To Sonja went the smaller piece, given to her by her father as a pendant. However, he would not reveal to her the truth to the pendant's true purpose. The other piece, the discus-sized larger piece, was kept hidden within Viktor's flesh, out of sight where Marcus could not see it.
The keys remained hidden until 2003, when Marcus was able to successfully combine them to release William from his entrapment.
- While according to Evolution, the keys were crafted by Selene's father, Underworld: Rise of the Lycans shows that Sonja had the pendant piece as a child, almost two hundred years before Selene's father was even born. This is likely a goof.