Marshal would be interesting but this may be an NPC that works on thier own.
Background: He works for a Verdant Prince (MM 4) on the plane of Thelanis (Eberron Campaign). He was met in one of the background sessions I run for my players (when we bring in new Characters/Players I always try to find time to run a lower level session of that one characters background) The background was for the Duskling Barbarian/Totemist in the party who was originally from Thelanis but was transported to Eberron by unknown means.
The session involved the PCs clan (the other players made up Duskling characters for this session) being poisoned and corrupted by an unknown source, the PCs were sent to investigate. After tracking down the source of corruption they met up with the Pixie and eventually subdue him/talk to him. He is unable to fix/help them but tells them how to summon the Verdant Prince, who appears and offers the PCs a way to heal thier tribe, they must kill the Shaman of the tribe. They make the oath and fullfil it, the Barbarian/Totemist takes the now empty position and the tribe is no longer corrupted. There are alot more details to the story but the basic premise is that the Pixie is Oathbound to the Verdant Prince and will eventually seek out the Totemist again.
Cheers,
E