Staff of the Adder

Staff, Uncommon, Requires attunement
You can use a bonus action to speak this staff's command word and make the head of the staff become that of an animate poisonous snake for 1 minute. By using another bonus action to speak the command word again, you return the staff to its normal inanimate form.
You can make melee attacks using the snake head, which has a reach of 5 feet. Your proficiency bonus applies to the attack roll. On a hit, the target takes 1d6 piercing damage and must succeed on a DC 15 Constitution saving throw or take 3d6 poison damage.
Attack: Strength modifier + Proficiency bonus to hit Damage: 1d6 piercing damage + DC 15 CON save against 3d6 poison damage
Modifications: The animated staff cannot be attacked and destroyed.