Nanlethos Moongrace is an oddity among the Priesthood of Elune. Perhaps its his gender; while males have been allowed to join the Priesthood since the end of the Third War, they aren't exactly common. More likely it is his 'race': A Satyr. Nanelthos Moongrace led a wicked life, there can be no doubt. He willingly traded his soul to the Burning Legion for greater power, becoming a Satyr, one of Xavius' twisted children. For thousands of years he lived a life of cruelty and Fel magic, becoming a ghost story of Ashenvale.
That all changed when the Burning Legion actually invaded (During the Legion Expansion). SOmething in him, perhaps the shred of morality that he long though dead and gone, rebelled and he fled that lifestyle. Alone, overcome by guilt and remorse for his wickedness, Nanelthos came upon a shrine to Elune, the Mother Goddess. There, in the light of the Moon, he was offered a choice: Serve Her and earn forgiveness, or reject Her and die alone. It was an easy choice for one who craved forgiveness and mercy, and he became a Priest of Elune.
Now he dwells in Stormwind, serving those Kaldorei who, for whatever reason, chose to remain in Stormwind rather than move with their fellows into Bel'ameth. He's an oddity of a Priest, generally taking pains to hide his corruption to put others at ease, and serves the Goddess willingly and happily. Here we see him brushing up on his theology and rituals.
Art by the lovely Emily Camissa: https://linktr.ee/emilycammisa