Mare Bello Fiore is a supporting character in Overlord.
Mare is an NPC created, along with his sister Aura Bella Fiora, by Bukubukuchagama, one of the 41 Supreme Beings of the guild Ainz Ooal Gown. He is a young dark elf and serves with his sister as 6th floor guardian of the Great Tomb of Nazarick. Like all the floor guardians, he is extremely powerful, being level 100 with levels in more than 5 jobs. He wears a skintight bodysuit of blue dragon scales covered by a white vest and pleated skirt, with his thighs exposed above white stockings and brown boots. He carries a jagged wooden staff called Shadow of YGGDRASIL. Mare is demure and prefers reading books to interacting with others. He always defers to Aura, as his creator stipulated that the younger brother should obey the elder sister (as part of a joke with her own brother).
Reason For Cross-Dressing
Mare wears the clothes that his creator dressed him in and continues to out of reverence for her. Though he recognizes it as strange, he believes it is a custom of the Supreme Beings for young boys to be dressed as girls. In reality, Bukubukuchagama likely made him a trap partly to play into his dynamic with Aura (who is by contrast a tomboy), and partly because she, as a voice actress for hentai games, liked traps.