The Sergeant is a Corpus boss found on Phobos. He currently has no name or associated lore. He speaks in the Corpus language, with his messages subtitled for the Tenno to understand.
"From pods you have come, in caskets you will go!"
"Orokin secrets cannot remain secret forever… start talking!"
"You call that skill? [clan] should be ashamed!"
"That [warframe] would look great hanging on my wall."
"This is your final warning, [name]. Leave this System at once."
"I grow tired of waiting, [name]. Will you face me?"
"Is this a gathering of the freaks?"
"I'm only just warming up."
"Fashion victims about to become murder victims!"
Before Update 16.4, the Sergeant was named Sergeant Nef Anyo and had character background narrated by the Lotus. His dialogue lines were identical. Currently, the name Nef Anyo belongs to another character, fully divorced from The Sergeant or his boss fight.
Lotus: "Sergeant Nef Anyo oversees operations of the Solar Rails in this district. Intelligence reports indicate that Anyo has been using the Rails to acquire recovered cryopods containing dormant warframes. Kill him and save your fellow Tenno."
Lotus: "Anyo is stockpiling the pods and selling them to the highest bidders. His clientele includes rogue scientists and splinter groups with nefarious intentions."
Lotus: "Anyo's self-interests are a threat to our ongoing operations. He must be removed immediately."
Lotus: "Eliminate Anyo. When the job is finished, we will send in a clean-up team to recover the pods."
Lotus: "Anyo's venture has afforded him the best in Corpus security robotics. Eliminate anything that moves."
Lotus: "We cannot allow the warframes to fall into the wrong hands. Taking Anyo out is imperative."
Lotus: "Anyo has too much at stake. He will fight to the death."
Lotus: "Anyo is aware of your presence. Get the jump on him."
Lotus: "Security has tightened in this section. You are nearing Anyo's position."
(mission complete) Lotus: "The death of Sergeant Nef Anyo should weaken the Corpus Research & Development operations for quite some time."