"Dopple" isn't anything, although that's not your fault. Technically it would be "doppel" if they were to shorten it. Anyway, doppel's just a weak mirror image of your rogue--it's pretty much useless at end-game, because its highest level is around 57-58 if my memory serves correctly, and attacks with a 2.0 speed no matter what you're buffed with. It can be useful for pulling things at times, but even then it's best to leave it one or none.
The Possession Beast quest chain starts at the mayor of Zakate; it will send you through areas of Turba and Parness, and will end at the Ruins of Lament.
Oh that thing... Yeah I don't have one on my rouge for some reason... I thought it was for the ranged class, didn't know a rouge can get/use it too.
I'm mostly used to be a WoW player and will probably go back to it someday. So all this talk of AA sounds rather noobish to me, and annoying. From the way you guys make sins sound, this game or the class sounds rather broken... I know in WoW only lazy afking noobs AA, and do the lowest DPS. Granted I'm sure it's different here but still same concept. Also I highly doubt you just chase people around in BF only using AA, isn't there stuns and crap you have to use as well? Because I highly doubt someone is just going to stand still while you AA them in melee range... From all this talk of AA and it being so "pro" makes me not even want to bother with the class anymore. :\