Joy was brought up by priests of Lathander together with her twin sister Light of Heavens. She is a dancer who takes pride in bringing happiness and light to the people and can be found at the Merchant's District in Neverwinter during Act III. Joy can be recruited to Crossroad Keep to serve at the inn to fulfill a quest given by Sal. She increases Keep income by 10%.
If you recruit Joy, her sister Light of Heavens, and also build the church of Tyr, she will give you the "Charm of Joy", a miscellaneous item that looks like an amulet. Just keeping her charm in your inventory will increase your Charisma by 3 and provide a +3 AC bonus vs. Evil opponents (as long as you are good-aligned or have high enough rank in the Use Magic Device skill).