Wizard Debt

From UnknowableWiki

Wizard Debt is created when a witch or wizard saves the life of another. The exact nature of this bond is unknown, but it's certainly a kind of ancient magic.

• James Potter saved Severus Snape's life in their sixth year, after a dangerous prank Sirius Black pulled off (PA18). This debatably still influences some of Severus' actions (PS17).
• Harry saved Peter Pettigrew when he suggested Pettigrew ought to die in hands of the Dementors rather than murdered by Sirius Black and Remus Lupin (PA19). In the end, Pettigrew escaped; the Dementors never captured him (PA20). Four years later, Harry reminded Peter of this, and the small impulse of mercy that Wormtail had resulted in his death (DH23).