The taurobolium was the practice of sacrificing a bull to the gods (usually Magna Mater and Attis) in ancient Rome.

“A man descends into a pit or trench, wearing a toga of which one fold covers his ribbon-adorned head. The pit is covered with an openwork platform or flooring with many holes in it. A bull is then brought and its chest hacked with blows from a spear.”

“The huge wound spouts a flood of hot blood…which seethes in all directions…Through the countless channels provided by the perforations a stinking torrent falls. The priest enclosed in the pit gets the full force of it, exposing his befouled head to every drop; his robe and his whole body reek. Worse is to come! He tilts his head backwards, exposing his cheeks, his ears, his lips and nostrils, even his eyes. Without sparing his palate, he soaks his tongue in it, until his whole body is impregnated with this horrible, dark blood.” (Prudentius, Peristaphanon, X, 1028-40).

“The victim is removed, the cover taken off, and the ‘the pontiff, dreadful to see’ is extracted from the pit. He is hailed ‘with the idea’ that vile blood…has purified him while he was hidden in these shameful depths.’…in the Roman era the process consisted of being immersed in the spilt blood in order to identify oneself ritualistically, though imaginarily, with the victim. It was a substitution sacrifice. Inscriptions inform us that the slaughtered bull’s testicles were cut off and buried beneath an altar, just as the vires [meaning nutsack] of the castrated galli were ritually interred. [Link]

There’s actually a scene in the awesome, but cancelled HBO television show, Rome, where Attia of the Julii participates in the ceremony and is suitably doused.

Bathed in the blood of a bull, mouth and nose filled—just completely saturated in gore. That must have been one hell of a visual.