Raising

The Raising was a ritual described in the Scrolls of Aberjian, by which Wolfram & Hart hoped to raise a being from Hell that would lure Angel from his mission ("To Shanshu in L.A.").

In order to steal back the scrolls and perform the ritual, lawyers including Holland Manners, Lindsey McDonald and Lilah Morgan hired a pair of monks to summon Vocah, "the bringer of calamity." He prepared the ritual after first slaughtering the Oracles and planting his mark on Cordelia, opening her up to endless visions and incapacitating her.

After finding from the spirit of one of the Oracles that the way to spare Cordelia was an incantiaion also contained on the scrolls, Angel followed the lawyers to the Raising, interrupting Vocah. As he fought the demon, Lindsey stepped up and finished the ritual.

It was revealed at the end of the episode that, in order to distract Angel from his mission (especially after he had seen the Shanshu Prophecy on the scrolls), Wolfram & Hart had raised his sire, Darla, nearly four years after he staked her in Sunnydale ("Angel"). As a side effect of such a ritual being performed on a vampire, Darla was restored to life, including the diseases that plagued her before being sired by The Master, as well as her human soul, but with the memories of the four centuries she lived as a vampire intact.

The Ritual
The ritual is performed with five vampires chained to a large box--a cage for the being summoned from hell. An incantation is read from the scroll. There is a portion that can be read in English and a portion that must be read in Latin (Manners complains upon arriving that Vocah has not even gotten to the Latin yet). While speaking of the vampires being held as part of the ritual, there is a call-and-response; the one performing the ritual speak of how there is no time for the five, and his attendants respond "Yet they live." Though Vocah's attendants are reluctant to respond in kind for Lindsey, they do so. Upon reaching the end of the Latin, the five vampires are exterminated, spontaneously dusting, one by one, as they are sacrificed to summon the being from hell.