Staff of the Adder

As a Bonus Action, you can turn the head of this staff into that of an animate, venomous snake for 1 minute or revert the staff to its inanimate form.

When you take the Attack action, you can make one of the attack rolls using the animated snake head, which has a reach of 5 feet. Apply your Proficiency and Wisdom modifier to the attack roll. On a hit, the target takes 1d6 Piercing damage and 3d6 Poison damage.

The snake head can be attacked while it is animate. It has AC 15, HP 20, and Immunity to Poison and Psychic damage. If the head drops to 0 Hit Points, the staff is destroyed. As long as it's not destroyed, the staff regains all lost Hit Points when it reverts to its inanimate form.