The Trial of Blood, sometimes called the Trial of the Body, is one of the three trials that a Quad Potential must complete on their Quad Quest.
The trial is designed to test a Potential beyond the physical realms of mortal people and prove they have the Quad magic within their body.
In Rhapsody Ejjina Mexonber-Quad is tortured almost to death, well beyond what would kill a normal person, by an Oferan named Adibolus, Son of Su'Bolus.