According to an ECHO log found aboard Sanctuary III, FL4K served as an Indexing Unit under the command of a man known as the Grand Archivist, sometime before the events of Borderlands 3. Their employment was cut short when FL4K suddenly acquired self-awareness and a thirst for murder, as FL4K puts it. At this time, it is unknown what brought about this sudden change in FL4K, or which archives FL4K and their master were responsible for.

After gaining self-awareness, FL4K now roams from world to world seeking self-discovery. While they feel a connection with the primal wisdom of animals (and thus always have a pet companion with them), the social constructs of humans are strange to them. FL4K has an unending goal to chase The Hunt, an apparent belief of hunting as a way of life; they pursue The Hunt in an attempt to please Mistress Death, a personification of Death itself.