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 improves traffic into the inn, but does little else.
If you recruit her, and her sister, and build the church of Tyr, she will give you a miscellaneous item that looks like an amulet. Merely keeping it in your inventory will give you the bonuses, as long as you are good-aligned or have high enough Use Magic Device.