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Nightingale Strife is a special power the Dragonborn can use once a day to automatically absorb 100 points of Health from a target during combat. It is received as part of choosing to become an Agent of Strife, one of three mutually exclusive rewards for the quest Darkness Returns. The Dragonborn may only choose one, the other two are Shadowcloak of Nocturnal and Nightingale Subterfuge.