Saūron

Saūron (サウロン, Sauron) is an Arrancar and Shinigami hybrid, born from the fusion of the Arrancar, De Soto, and Mod Soul, Auron, both of whom were created by Charles McTavish for the sole purpose of growing in power and becoming what we know now as Saūron. While he carries both the memories of Auron and De Soto, the latter's personality seems to be more dominant.