The Masked Arrancar is a mysterious being who was known as "El Santo Verdugo", but was called Santo by everyone, and served in Aizen's Arrancar army as an Espada before the several of the current Espada's were even in their positions. Yet he soon became a Privarron Espada as Aizen began using the Hōgyoku to create more powerful Arrancars. After Aizen's defeat at the hands of Ichigo Kurosaki, Santo ended up joining Tier Harribel along with other Arrancars in order to rebuild their devastated and to see where it might lead him.