Venomous Lamia

Your fangs exude a powerful serpent venom drawn from deep within your curse. You can use a bonus action to envenom your fangs. The next time you hit a creature with an unarmed strike using your fangs before the end of your next turn, the target takes an extra 1d6 poison damage. This damage increases to 2d6 poison damage at 8th level and to 3d6 poison damage at 16th level. You can use this feat a number of times equal to your proficiency bonus, regaining all expended uses when you finish a long rest.