"Objective achieved. Move to extraction."
Zer0 was salvaged and restored (as a hobby by a Legionnaire robotics mechanic), and most off his systems were rebuilt. As a result, he doesn’t know where he’s from, who his people are, or what his purpose is meant to be.
Legion records are spotty; drones of his kind are unknown, and the technology employed and intact is not unique to any known race, being a conglomeration of systems similar to several other known races. He is presumed unique (subject to further discoveries).
Local authorities have a range of legal opinions on the matter of wholly-artificial lifeforms, ranging from “abomination” to “useful with the proper inhibitors”. Only the Legion accepts Zer0 is a fully sapient being, regardless of his origins. Elsewhere, he can expect to hear “we don’t serve those here! your droid will have to wait outside!”
What he doesn’t know: the Machine Intelligence threat is galaxies-wide and over a long enough timeline, tries everything. Zer0 is one of those attempts. His original purpose presumed lost (it might be), his original manufacturer unknown to him. Zer0 is an infiltration unit on the scale of local lifeforms: humanoid, roughly 2m tall, roughly 100kg. His appearance sets him apart from lifeforms: he is obviously a constructed being. Whether this was intended or merely due to the accident that left him behind to be discovered, I haven’t decided.