Seeking a mature guild (Preferably RP)

So I've had GW for a few years now, but after completing the original I took a long hiatus and have been playing WoW and EVE since.

I'm looking to get back into the game, and now own Factions and Nightfall. My main character now is a level 18 R/E, so I'm not sure how useful I'd be in endgame, but I would very much like to experience some of the harder stuff.

I'm seeking a mature, preferably large guild that'd be willing to take me to see this sort of thing. An RP guild would be a bonus, but not required.

(Also, I intend to get EotN within a month or two.)