Blessed of Corellon

Corellon Larethian was an androgynous being who can change form at will, as could the ancestral elves. Naturally, 'Some elves retain a blessing of Corellon. As part of this blessing, these elves can actually choose their biological sex whenever they finish a long rest. These elves can choose to be male, female, neither or both based on their moods or feelings.