Bane Arrow

This arrow appears as a broadhead arrow with jagged serrations and a rune on one side and an ourobouros on the other side. 

The arrow requires an attunement ceremony during which the blood (dried or fresh) is painted on the serrated broadleaf head of the arrow after which it is ritually fitted into firing position on the bow it is to be fired from by the firer. All three items become linked until used. The ceremony takes a short rest during which time the rune glows white hot and then fades to a dull red and then changes to a likeness of the individual creature to which it has it has attuned and an ourobouros appears on the bow and the outside of the firer's dominant hand. The attunement of the arrow can be canceled by breaking the arrow or bow; if the firer is knocked unconscious; or, if the bane creature is killed.

After attunement the firer gains advantage on attack rolls when using this arrow against its bane creature. The firer can ignore half cover. Three quarters cover counts as half cover.  If the ammunition strikes the bane creature, an additional 2D6 necrotic damage is delivered and the creature must succeed on a DC 15 Strength saving throw or be knocked prone.

Once it hits a target, the arrowhead is no longer magical. If it misses, the magic is not discharged.

Proficiency with a Longbow allows you to add your proficiency bonus to the attack roll for any attack you make with it.

Notes: Damage: Necrotic, Advantage: Ranged Attacks, Ammunition, character to fire the arrow., Damage, Combat, Bane, Ammunition, Heavy, Range, Two-Handed, Slow