In the early episodes of The Mandalorian, it seems like our villain is the Client seeking Baby Yoda — but the real baddie in charge, we soon find out, is Moff Gideon. The former Imperial commander is the most terrifying threat to our hero and his allies, and in the season one finale, we find out something else: he was personally involved in the slaughter of Mandalorians during the Rebellion. Played by Giancarlo Esposito, who previously played another terrifying baddie on Breaking Bad, he's the latest in a long line of intimidating Star Wars villains.
Gideon uses the old Imperial title of "Moff," which dates all the way back to the original A New Hope and its villainous Imperial officer Grand Moff Tarkin. Moffs are essentially the Imperial equivalent of a governor, but on a bigger scale: they're placed in command of entire sectors of space under Imperial rule, and they're given almost free rein to do as they please with the planets under their rule. While the Imperial moffs are abolished by the time of The Mandalorian, it's clear that Imperial remnants still obey the old hierarchy, given the scope of Gideon's command.
As we learn, though, Moff Gideon isn't just any Imperial officer — he has a very specific connection to the Mandalorians. He was part of the Imperial Security Bureau, which was the intelligence arm of the Empire, in charge of ensuring loyalty by any means necessary. In this capacity, he was one of the officers leading the Great Purge, aka the Night of a Thousand Tears, during which Imperial forces murdered the majority of the Mandalorians on their home planet in punishment for their Rebel sympathies and drove the rest into permanent hiding. Gideon took a personal role in those killings, apparently, to the point where our Mandalorian hero knows him by name and reputation already. He's apparently continued to hunt down the survivors of Mandalore, including the community on Nevarro, who are completely wiped out (except for the Armorer) on his orders.
It doesn't look like Moff Gideon will be going away anytime soon, either. The finale's cliffhanger-y final moments show that Moff Gideon survives the crash of his TIE fighter, and he's more of a threat than ever: not only is he still alive and angry, but he somehow possesses the Darksaber, a famous black-bladed lightsaber traditionally wielded by the leader of Mandalore. When The Mandalorian season two debuts, we're sure Moff Gideon will be more of a threat than ever!