The Oathbow by hyper365

The oathbow may only have one sworn enemy at a time. Once the wielder swears to slay a target, he cannot make a new oath until he has slain that target or seven days have passed. Even if the wielder slays the sworn enemy on the same day that he makes the oath, he cannot activate the oathbow’s special power again until 24 hours have passed from the time he made the oath