Backstory help with Assassin's Guilds in Golarion

[Cenorin]

I have a player interested in playing a CN rogue with a penchance for artwork trained by a guild of assassins. The Red Mantis seem too evil and don't work with his backstory for other reasons, but the Guild of Wonders sounds potentially promising. Is there any information about them beyond what's available in the Guide to Absalom?

I'm also open to other suggestions for assassin's guilds or other groups that he might have trained with.

[Cpt_kirstov]

I think Riddleport has an assassin's guild. And being a fence for plundered artwork might fit that background and explain why he's traveling.