The Mu Codex
Steal book from Ghost Widow
Glad to see you. We've got a job. Seems someone's hired us to steal some old book from Ghost Widow's faction. Called the Mu Codex. Who's hired us, you ask? Why, Mako's faction! That's right, those Arachnos factions are always at each other's throats. You'd best remember that if you ever decide to get involved with their lot. Trust no one.
Oh, there's one more thing I didn't tell you. I'm planning to keep this book for myself. So wipe out everyone in the Arachnos lab, won't you? It's the only way we can get away clean.
Arachnos Base @ Mercy Island (Arachnos)
Objective: You stole the Mu Codex
Mission Complete: You stole the Mu Codex
Ah, the Mu Codex. This'll fetch a pretty penny. Oh, don't worry. Mako will believe that Ghost Widow managed to keep the Codex from us. It'll give him a good excuse to call her out, which is what those elite Arachnos operatives like more than anything. They just love their petty intrigues!
Of all of them, only the Arbiters are above all that in-fighting. Heck, even I respect the Arbiters to a certain degree. You may want to check them out.