Young Adult, Synthetic, Mobile Infiltrator and Nocturnal Exterminator Unit Six is or was (pending evidence of its destruction) a member of the original batch created to prove the viability of the program. Though plagued by persistent faults like many of other early models, Six is widely regarded as a success and boasts an impressive service record despite initial assessment which predicted a six month expiration date.
When then Teresa Palamara first approached the Wellington group about the YASMINE program, she was physically whole, though emotionally unstable due to the death of her mentor. Normally Miss Palamara would have been passed over after failing the psychiatric evaluation, but her other talents quickly earned her a place on the fast track instead. She not only had remarkable and almost intuitive skill as a martial artist, but her athletic prowess was nearly unrivaled by other applicants. At that time, the Wellington group was not yet differentiating between normals and those imbued by supernatural ability, but later 'interviews' confirmed the suspicion that Six had been a slayer (see Watcher's Council file).
Scheduled for a complete mind wipe a year prior to its disappearance, the likelihood of past memories interferring with its latest mission in Sunnydale California is rather high, but was deemed at the time to have a negligible effect on Six's ability to complete it and its wipe was delayed yet again. In retrospect, this appears to have been ill advised though investigations into the relationship between Six and its handler and allegations of misconduct inherit in such fraternation are still ongoing.
Though rumours persist of Six going rogue, the Wellington group has maintained its stance that the unit was destroyed and will be recovered shortly. Two years have passed.