Translating to “spirit of life” and taken from its original form “Spiritus Mundi” (spirit of the Universe), Spiritus Vitae refers to the interaction between the cosmic forces and the matter of the human body.
Sam confirms Dean's suspicion that they are dealing with a witch. He tells Dean that they are dealing with a shtriga, a kind of Albanian witch with legends that date back to ancient Rome, that feeds of off spirtus vitae. Confused as to what spritus vitae is, Sam tells Dean it is Latin and translates to "breath of life" -- a person's life force or essence.
In order to get Sam and Dean to stop performing the trials, Crowley begins killing all the people the Winchesters have saved. While Crowley is on a blind date with Sheriff Jody Mills as "Roderick," Jody excuses herself to the bathroom. While she is gone Crowley sets up a spell and begins chanting a death spell.
Manu mortis accesso spiritus vitae recedit.
A witch in Wichita, Kansas, was taking runaway girls in and giving them a new life. She gave each of them a pendant, which unknown to them, steals their life force until their bodies wither away. The witch used this to keep herself young. The Apocalypse World hunter Jules is able to locate and kill the witch, but the curse starts rapidly taking her latest victim, Lora.
Jules and Castiel try to reverse the hex with a spell, but the spell accelerates the process and Lora dies. Jack soon comes to the realization that the pendant the witch gave the girls is what is cursed and is still taking Lora's life force, as the pendant the witch was wearing was still working to try to keep her alive, but it wasn't healing her because the witch-killing bullet was still inside her. Jack takes the witch's pendant and smashes it with a hammer, releasing Lora's life force and returning it to Lora's pendant, causing her to return to life.