The Twinheaded Serpent Bow

This Longbow is decorated with two serpent head
in each end of the bow. The handguard is fitted
with a piece of metal where two snake tail meet.
ABILITY: Before you make an attack with the
bow, you can charge the shot, and make a magical
arrow fire from the bow. When the arrow hit
the arrow turns into a snake and inject
3d6 poison damage in the wound. The target
makes a CON SAVE DC:13.
On a succesful save, the target take half damage.
The Bow have 3 Charges per long rest