Mas Amedda was the Grand Vizier of the Galactic Empire. As Grand Vizier, he managed the day-to-day operations of the Empire. He was also the head of the Imperial Ruling Council and a personal assistant of Emperor Palpatine.
Before serving the Empire, he was the Vice Chair or Vice Chancellor of the Galactic Republic under Supreme Chancellors Finis Valorum and Sheev Palpatine.
Mas Amedda would preside over the senate during debates and worked behind the scenes to ensure that the orders of Chancellor Palpatine would be adopted. As a close acquaintance of Palpatine, he was aware of some of his darkest secrets.