Bloodbow

This longbow is carved of a light, sturdy wood such as hickory or yew, and it is almost always stained a deep maroon hue, lacquered and aged under layers of sundried blood. The bow is sometimes decorated with reptilian teeth, centaur tails, or other battle trophies. The bow is designed to harm the particular type of creature whose blood most recently soaked the weapon. When you make a ranged attack roll with this magic weapon against a creature of that type, you have a +1 bonus to the attack and damage rolls. If the attack hits, the target must succeed on a DC 15 Wisdom saving throw or become enraged until the end of your next turn. While enraged, the target suffers a random short-term madness.