[quote=@Irisity]
I like it, but who they spying on?
[/quote]

Everyone!

Nah, jokes aside, I figure the character would be useful when the [s]party[/s] crew need to have a little bit of tact when trying to procure something (like say a ship full of gold) or when some clever reconnaissance work needs to be undertaken. The way I see it, when you're doing potentially bad things (or even good things), sometimes you need someone who can fight and other times you need someone who can accomplish a task with the utmost discretion.

Another valuable trait of said character would be connections to people who deal in information. Say for example, a most beloved crew-member is captured, well how does the [s]party[/s] crew find them? Perhaps, the mysterious spy can ask some old colleagues to ask the right people the right questions?

[quote=@Irisity]
Who hired them?
[/quote]

Nominally, the spy would work for the Captain...although who knows? Can you ever trust a spy? :D