Nebula is a Earth Fairy. Nebula was once the Major Fairy of Peace, but soon became the Major Fairy of Vengeance after the Wizards of the Black Circle trapped the Earth Fairies in their own realm. Later, at the end of Season 4, Morgana, the ex- Queen of Earth Fairies handed over her crown to Nebula, since Princess Roxy was too young to be queen.  

Nebula, after becoming the Major Fairy of Vengeance.