Struggling a bit to find templates to apply to an invisible stalker.
Concept is that, before Yan-C-Bin was open about his intentions to eliminate all rivals to his dominion over the Plane of Air, he invited the Great Caliph of the Djinn and Chan to work with him to create a being of purest air. Yan-C-Bin secretly corrupted their efforts, though, slipping into the ritual a way to control the new elemental - which, in turn, allowed mages and arcanists to bind the invisible stalkers of whom the first invisible stalker is progenitor. He turned the first invisible stalker into his assassin, his thief, and his spy, leaving the invisible stalker no choice in the matter as Yan-C-Bin used the invisible stalker to incriminate Chan in his crimes against the Great Caliph and the Great Caliph in his crimes against Chan, hoping that, when the dust settled in a battle between the two, he could finish off the weakened victor. The invisible stalker, however, was sealed away before Yan-C-Bin's plans could come to fruition.
The invisible stalker struck a deal with Ao when he was released - he is now free of the hold Yan-C-Bin and those others might have over him... and if he succeeds in the task, Ao might free the other invisible stalkers from the weakness that allows arcanists to bind them.
Thinking True Neutral or Chaotic Neutral fits best - Which is unfortunate because the demonically infused template which would give him constant haste (great with swiftblade) would require him to be chaotic evil. Not particularly interested in having him wrestle with/angst over a demonic side, either. So. Suggestions, given the backstory, anyone?
I could always just advance his racial hit die - I would get a small benefit of... 8 more HP if I use his remaining 4 LA on racial HD, but it's the only benefit I'd see for using racial hd instead of a template.