Fics like Oathbreaker

Christina the Pure is the most famous member of The Order of the Radiant Sun, a chivalric order of knights and paladins dedicated to helping those in need. Loved by the populace, she quickly becomes a full-blown paladin and gains access to holy magic, despite her relatively short time within the order. In exchange, all she has to do is uphold her oath to preserve her virginity for as long as she's a member. But her lack of time means a lack of experience, and when she charges headlong into what should have been a quick and easy battle, she learns the hard way what happens when you underestimate a trio of succubi who have a thing for women in armor...