Mas Amedda is a Chagrian male from Champala, first appearing in The Phantom Menace (1999) played by Jerome Blake. He is in every prequel film, standing at Palpatine's shoulder in the Senate, and he speaks perhaps a dozen lines across the trilogy.
The machinery of the coup
As Vice Chair of the Senate he is the procedural instrument of Palpatine's rise: it is Amedda who steers the chamber, who prompts Jar Jar Binks toward the motion granting emergency powers, and who converts a constitutional republic into a war government using nothing but order of business. He later oversees the Strategic Advisory Cell and its weapons programmes, the Death Star among them.
Grand Vizier
Under the Empire he becomes Grand Vizier, running the civil bureaucracy while the military runs everything else. The Aftermath novels are unkind to him and correct to be: after Endor he is a figurehead with no fleet, kept alive and in post by Fleet Admiral Gallius Rax because a puppet with the right title is administratively convenient.
The Galactic Concordance
His last significant act is signing the instrument of surrender that ends the Galactic Civil War. Rather than face prosecution he is left to head a powerless provisional government on Coruscant — the Empire's most senior surviving civilian, remembered as a sycophant who outlasted everyone he flattered.
