- Travers: "The Cruciamentum is not easy for Slayer or Watcher. But it's been done this way for a dozen centuries whenever a Slayer turns eighteen. It's a time honored rite of passage."
- Giles: "It's an archaic exercise in cruelty. Locking her in this tomb... weakened, defenseless... unleashing that on her."
- — Quentin Travers and Rupert Giles[src]
The Cruciamentum, officially referred as Tento di Cruciamentum, was a rite of passage practiced by the Watchers Council to test the Slayer if she lived to see her 18th birthday. While some of the more conservative members of the Council considered it a time-honored rite of passage, other less ruthless Watchers considered it to be a brutal, antiquated practice, Giles describing it as an "archaic exercise in cruelty."
- "It's a test, Buffy. The Tento di Cruciamentum. It's given to Slayers when they reach - if they reach their eighteenth birthday."
- ―Rupert Giles[src]
In the weeks prior to the Slayer's 18th birthday, Watchers were forced to inject the Slayer with chemicals such as muscle relaxants and adrenaline suppressors, which gradually weakened her powers until she had the average physical abilities of a human, if not even weaker. Watchers were also ordered to keep the Slayer unaware of the test. Afterward, the Slayer would be taken to a location selected by the Council and pitted against a particularly dangerous vampire. The intent of the practice was to establish the Slayer's intelligence and practical capabilities, testing her ability to out-think her enemies as well as outfight them.
Buffy Summers' Cruciamentum
- "It's an antiquated exercise in cruelty. Locking her in this tomb... weakened, defenseless... unleashing that on her. If any one of the Council still had actual contact with a Slayer they'd see. But I'm the one in the thick of it."
- ―Rupert Giles to Quentin Travers[src]
In 1999, Buffy Summers was pitted against Zachary Kralik, a psychotic vampire who had been a serial killer in life. However, the test was jeopardized from the beginning due to Rupert Giles's attachment to his Slayer - resulting in him telling her about the test when she was supposed to be kept in the dark about it - and Kralik escaping captivity, siring one of the Council employees assigned to monitor him while killing the other, and abducting Joyce Summers, the mother of the Slayer.
Buffy was eventually able to defeat him by taking advantage of his reliance on anti-psychotic pills, switching the water he took with his pills with Holy Water, causing him to burn up from the inside. Though Buffy was successful, Giles was ultimately dismissed from the Council for his interference in the Cruciamentum and for his emotional attachment to Buffy.
It was implied by Wesley Wyndam-Pryce that some Watchers may undergo a similar test; when the staff of Angel Investigations regressed to their teenage personae after a spell went wrong, Wesley assumed that they had been locked in the Hyperion Hotel to track down and kill a vampire, showing no sign that he ever speculated on the possibility of Cordelia Chase or Winifred Burkle being Slayers themselves and simply focusing on such evidence as the available weaponry and his own knowledge, even noting that the test was usually performed on Slayers without saying that it was only for them.
To train them in the first against The First Evil, Buffy and Spike locked several Potential Slayers in with a vampire, hoping their Slayer training would be enough to overcome their relative powerlessness in regard to the vampire, the exact method behind the Cruciamentum.
It was later revealed that Giles and some peers of his, during their time at the Watchers Academy, were given a similar test where they were to take on the "Highgate Vampire" in the infamous cemetery in London. However, the Highgate Vampire turned out to be a Lorophage Demon which siphoned out all of the trauma out of the heads of all of them but Giles, massacring them all.
- Buffy Summers: Faced Zachary Kralik at the Sunnydale Arms, after Kralik abducted Buffy's mother, although this happened after the Watchers lost control of Kralik. Buffy managed to switch the water Kralik used to take his anti-psychotic pills with holy water.
- Buffy and Spike subjected a number of Potential Slayers (Vi, Rona, Kennedy and Molly) to something similar, locking them in a crypt without a vampire and expecting them to either use their Slayer training and cunning alone to defeat a vampire or to die powerless.
- Catherine Callan: An Irish Slayer, active from 1873 to 1876; faced prejudice from the Watcher's Council.
- Millicent Rose Gresham: Stage name Fatima Araby, she traveled with a carnival; the vampire that she was supposed to face was killed by Blasko, a former Watcher, who proceeded to kill Millie's Watcher and the reviewing Council members before Millie outsmarted him.
- Dorothy Singers: Faced the Cruciamentum in 1919, her Watcher suffering from a serious mental illness.
- Zoë Kuryakin: A Beatnik in New York in 1952, Zoë's Watcher, Ian Sykes, arranged for her to face the turned Watcher Creighton Faust, feeling alienated from her due to her lifestyle; Zoë killed Faust and Sykes, but, having been bitten and sired during the fight, walked to an area where she could be exposed to the sun so that she would not become a vampire herself.
- Beryl McKenzie: Joined a commune in Nova Scotia in 1970 before coming into her powers; faced the Cruciamentum as her initiation into her role as a Slayer.
- Nikki Wood: Pregnant during her Cruciamentum in 1973; her Watcher, Bernard Crowley, objected to making her endure the ritual in this condition.
- Peri Bohr: Fought her recently-turned and starving friend Julie Lemmer in a mall.