Hymenaios

Hymenaios is the Greek god of marriage ceremonies, an attendant of Aphrodite, as well as a frequent playmate of Cupid and Ganymede.

Percy Jackson's Greek Gods
Hymenaios showed up in person to lead the procession during the wedding of Orpheus and Eurydice. However, he could most likely already see that their marriage was destined to come a tragic end very soon, since he arrived wearing funeral black robes, while his sacred torch spluttered and smoked, with him shedding quite a few bitter tears during the ceremony.

Abilities

 * Hymenaios presumably possesses the standard powers of a god.
 * Amokinesis: Hymenaios has absolute control and divine authority over love, passion, and desire, though not as much as Aphrodite or Cupid, since his powers are only limited to wedding ceremonies.
 * Matrimony: As the God of Marriage Ceremonies, Hymenaios most likely has some special powers pertaining to marriage and matrimonial happiness, though his are most likely not as powerful as those of Hera.
 * Matrimony Precognition: As seen in Percy Jackson's Greek Heroes, Hymenaios could foresee that the marriage of Orpheus and Eurydice was destined to come to a tragic end.