Dot Pixis was the Garrison's former Chief Official of the Southern Territories, which includes Trost District. He was often simply addressed as "commander". In matters of defense, he was given full authority.
Sometime after ingesting Zeke's spinal fluid, Pixis was transformed into a Pure Titan during the Marleyan surprise attack on Shiganshina District.
Pixis was a bald man with a structured build. He had a distinguished mustache, with light skin and notable wrinkles under his eyes. As a commander, he also wore a bolo tie, much like his fellow commanders Hange Zoë and Nile Dok. As a high ranking Garrison officer, he was only seen wearing his Garrison uniform paired with a white button-up shirt and a red sash with gold trim.
Appearance: Pixis was a bald man with a structured build. He had a distinguished mustache, with light skin and notable wrinkles under his eyes.
Personality: Pixis was an eccentric man. " He retained a calm, and light-hearted demeanor, even in the midst of chaos, and he understands the strife and suffering of others, as he was seen allowing soldiers who wanted to leave because he understood the extreme amounts of terror and fear in those soldiers.
Dot Pixis in the story: After it is discovered that Eren Yeager can transform into a Titan, Eren is sentenced to death. Pixis, however, happens to be nearby when Armin Arlert gives a passionate speech in defense of his friend, vouching for the strategic and tactical benefits that he can bring to turn the tide of the battle. The officer in charge, Kitz Weilman, is not swayed, but as he is about to give the kill order, Pixis stops him, believing Armin's words.
Relationships: Erwin Smith - Pixis shared a similar view with Erwin that the current government was corrupt and unsuited to rule humanity, but that he would only help if his intentions were noble. Eventually, Erwin's plea and the resulting actions of the government would be enough to convince Pixis to participate.
Source: Attack on Titan Wiki, available under CC BY-SA 3.0.