The Oath of Running Blood

Vampire the Requiem - Covenant - The Invictus

The simplest of the supernatural oaths of performance, like the Blood-Tell Oath, requires a mystic trick that can be taught to any Kindred in a single night. While swearing the oath, the Kindred bleeds a single Vitae into a suitable vessel, generally a clear bottle of some sort, and expends a point of Willpower. When he expends the Willpower, the blood hardens into dark brown glass. As the Kindred nears to the fulfillment of his Oath, the blood becomes more scarlet and more fluid, turning fully liquid when the Oath is fulfilled.
The liquidity of the blood is based on the mind of the sworn subject. If he believes he is close to fulfilling the Oath, the blood becomes very fluid. If he knows in his heart that he is doing nothing to fulfill the Oath, the blood hardens back to solidity. It is thus possible for the blood to become completely liquid even though the Oath has not been fulfilled, if the Kindred in question thinks that it has.
If the subject suffers Final Death, the blood turns black and shatters into dust.
In the treasure room of an ancient Invictus of Spain rests a crystal phial, contained in a golden reliquary encrusted with gems. The phial contains the blood of Rhadeghund, a Mekhet who swore to find a way for the Kindred to shake off their Curse. She swore that Oath in the fifth century, and the blood in the phial has streaks of red liquid to this night. Once a year, on the seventh of February, the owner presents the phial to the other Invictus of the city, who confirm that the Oath is not yet fulfilled.

This power costs three experience points to learn, but only one of the participating Kindred — the lord or the vassal — needs to know the power to activate it.