While the term Ascension and its method was not coined and developed until 1804, the main process of turning mundanes into Shadowhunters through the Cup has been going on for centuries, the first known instance of which was when Jonathan Shadowhunter drank from the Cup. He was then followed by David, Abigail, and the many first Nephilims of the world.
The option is open to lovers and adopted children of Shadowhunters, and, in some rare cases, other Sighted mundanes interested or selected to become a Shadowhunter.
Drinking from the Cup was dangerous and did not always work. It is said that it takes special strength and resilience to survive the transition, thus prospective Ascendants must be extensively tested before they are even considered for the process.
The potential Ascender must be petitioned and appealed to the Clave. In most cases, the Shadowhunter acquainted with the mundane apply on his or her behalf. The Clave will then consider the petition for at least three months before approval, during which the history of the Shadowhunter who had applied, as well as his family's, is reviewed, and the background and nature of the possible Ascender is examined and evaluated. Essentially, this is done without the knowledge of the Ascender (if the applicant has no prior knowledge of the Shadow World as it is still illegal, save for some cases; e.g. the mundane has the Sight or was once a Downworlder) until the Clave decides to grant the petition. The Ascender is then told about his/her situation and is then given another three months to train and study to learn about Shadowhunter Law, culture, and that of the Shadow World.
After the Dark War, several mundane applicants (all of whom were told of their situation beforehand) were sent to the Shadowhunter Academy for training and lessons.
Once they are deemed ready, the Ascender is given to drink from the Mortal Cup and made a Nephilim, before or after which the new Nephilim would have to speak an oath, either with or without prompting.
Adult Ascendants who drink from the Cup are either unaffected by the process entirely or killed outright. When the process does not work, for whatever reason, the Ascendant is put through extreme pain, before finally dying with black veins across their charred skin. Because of the risks, the Council, at one point, considered lowering the age of agreement to Ascension to twelve or fourteen. While it does mostly work on children, adults who have successfully Ascended is not completely unheard of.
Either way, if the Ascender survives this process, he/she is rendered a full Shadowhunter. Mundanes who Ascend to become a Shadowhunter may then create and submit their own Shadowhunter last name for approval, or just choose from one of the defunct Nephilim names.
The method of Ascension was first developed in 1804, after the law prohibiting the intermarriage of mundanes and Shadowhunters was revoked after it was realized that interaction between the two kinds was unavoidable.
When the Cup was lost and believed to have been destroyed in the late 20th Century, the Nephilim believed that Ascension will never happen again and had become somewhat of a legend, until it was found and retrieved almost two decades later. After the Dark War of 2007, the Clave became desperate for new Shadowhunters after their numbers were depleted, and they reopened the Academy for new recruits, which include several children of Shadowhunters who have left the Clave and mundanes being trained to become new Shadowhunters through Ascension.
- Sophie Lightwood (1878)
- Dean Ashdown's husband (late 1800s)
- Gen Almodovar (2010)
- Thomas Daltrey (2010)
- Marisol Garza (2010)
- Simon Lewis (2010)
Potential candidates who either failed to Ascend, quit before they could go through with the ritual, or whose Ascension status remain unknown (accompanied by the year they started training for Ascension):
- Esme Philpott (1899)
- Mike Smith (1899)
- Boris Kashkoff (2008)
- George Lovelace (2008)
- Leilana Jay (2008)
- Sunil Sadasivan (2008)
- Milla (2009)
- While the process of Ascension did restore Simon Lewis's memories, it is unclear whether this was a result of the ritual itself, or if becoming a Shadowhunter affected—or undid—the demonic magic used by Asmodeus to steal them.