Wraith Waltz

You summon spectral energies to dance around you in a haunting waltz. Until the end of your turn, these ghostly apparitions provide an ethereal shield, granting you a +1 bonus to your AC. Additionally, any creature that enters your reach or starts its turn there must make a Wisdom saving throw or suffer disadvantage on its next attack roll until the start of your next turn. Undead creatures have advantage on this save. The dance fades at the beginning of you next turn

This spells AC increases by 1 when you reach 5th level (+2), 11th level (+3), and 17th level (+4).