The Cup is a gilded, glassine chalice carved from adamas and dipped in gold, and is the size of an ordinary wineglass, though heavier.
When Jocelyn drew the Ace of Cups of the tarot deck in which she hid the Cup, the golden Cup was held up by a hand in front of a rayed sun. The drawn Cup was adorned with rubies and smaller suns, unlike its true plain appearance.
Because of its mysterious transformative properties, drinking from the Cup turns mundanes into Shadowhunters. It is presumed that it became sacred and magical after Raziel used it as the vessel for his blood, imbuing it with his vast angelic power.
However, drinking from the Cup has its risks and does not always work. The Cup is most effective on children; in adults, it may either kill them or have no effect whatsoever. Because of this, only specially selected mundanes are allowed to drink from the Mortal Cup, since many never survive the transition. It takes special strength and resilience to survive the process, and because of this, the mundanes must be extensively tested and evaluated before they can drink from the cup and Ascend.
The Cup can also be used to help end the suffering of a person who turned Forsaken. The Forsaken must be forced to drink from the Mortal Cup, and its power would eliminate the pain from the Marks. It may either turn the Forsaken into a Shadowhunter or let the person suffer the negative effects of the Cup, which may ultimately lead to death.
A demonic counterpart of the Cup, the Infernal Cup was forged in 2007. Instead of angel blood, the Infernal Cup's ichor donor was the Greater Demon, Lilith, which gave it its demonic alliance. This gave the Cup the power to turn Shadowhunters into their demonic counterparts.
When the Angel Raziel was summoned, he mixed his blood with that of Jonathan's within the Mortal Cup. Upon drinking from it, Jonathan became the first of the Nephilim. The Cup was left with him, and over time, more drank from the Cup; those who drank the Angel's blood became Shadowhunters, as did their children and their children's children.
Given its angelic alliance, the Mortal Cup has different effects on Downworlders than it does on mundanes, as a result of their demonic heritage or disease. Downworlders who drink from the Cup will vomit up its contents and possibly die of paroxysms, due to their demonic aspects warring against the angel blood they ingested. If forced to continue drinking from the Cup, the contents will eventually burn the life from them entirely.
During the Hunts of the 16th Century, the Cup was used as a form of capital punishment, in inquisitional torture and murder, on Downworlders. Back then, this form of punishment was considered by the Clave to be just and merciful, because it infused the Downworlder with angelic power before death. This barbaric practice was made illegal in the Second Accords of 1887.
Instances of use
- Through the years, the Cup has been used to create more Shadowhunters when their ranks were depleted.
- In 1878, Sophie Collins underwent Ascension and drank from the Cup to become a Shadowhunter.
- In the 1990s, Valentine Morgenstern stole the Cup and intended to use it to create a new race of Shadowhunters. Jocelyn later retrieved this and hid it in a tarot card, and the Cup was believed by the Clave to have been destroyed in the Fairchild manor fire in 1992.
- In 2007, Clary Fray found the Cup, but Valentine later reclaimed it. He used it to summon Raziel, in hopes of compelling the Angel to bless his cause. Valentine threw the Cup and the Sword into Lake Lyn, the Mirror. Raziel then rose from the lake, bearing the Cup and Sword and brought the Instruments back to the shore, to later be retrieved by the Clave.
- Near the end of 2007, the Mortal Cup was used on the Endarkened Amalric Kriegsmesser in an effort to cure him and return him to a Nephilim. Unfortunately, drinking from the Cup ultimately destroyed him.
- Some time between 2008 and 2009, Simon Lewis and the first batch of Academy students in over a decade underwent Ascension and drank from the Cup to become Shadowhunters. One suffered the Cup's bad effects and died.
- According to the Shadowhunter's Codex, it was water in the Cup that the first Shadowhunters drank from the Mortal Cup.