Hi this might be a *spoiler* question so i'll use that just in case.
anyways I'm having trouble exposing Sarevok in the Ducal Palace, i have all the evidence i need, yes i did the Iron Throne, and rescued Duke Eltan, I have Sarevoks diary. hell i don't even know if i'm suppose to be at Ducal or Candlekeep. I'm on chapter 7 just to let you know.
anyways, heres what happens, i go to Ducal Palace and after that long winded dialouge,
and a lot of greater dopplegangers,i get my rear handed to me by Angelo, before that,
Sarevok is saying i failed. May i ask what i did wrong and what the solution is?
thanks,
RD

Were both of the actual Dukes alive after you beat the doppelgangers? Without them, it's just your word versus Sarevok's and Angelo's. Since he's the new political star and you're a wanted man, well.....

I saved Duke eltan, i have no idea who the other duke is?

In the palace, where Sarevok is getting ready for his coronation ceremony, there should be a group of nobles close to Sarevok (these guys turn into the dops). To the upper right of that group are two dukes: Belt and Jiia. Once you defeat the dopplegangers, you should show Sarevok's diary to Belt. This will prompt Sarevok to attack and when you beat on him for a while, he'll escape with the help of a wizard who shows up just in time to teleport him away.

ah ok, thanks, that was the solution i was looking for, see i wasn't sure if i should even be at ducal or not, that confirms that i need to beat the dopllegangers before they kill the 2 other dukes

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You need to show Sarevok's diary to one of the dukes after killing all the dopplegangers who will transform and attack the dukes as soon as your group enters the room. It is essential to keep at least one of the dukes alive. The easiest way to accomplish this is to haste your party before entering the room and rush 3 characters through the north door and 3 characters through the south door (to avoid a Marx Brothers jamup.) This will give you a brief moment before the dopplegangers transform and attack. Now the key here is to surround the two dukes with summoned creatures - lots of summoned creatures. This will give your heavy hitters time to kill the dopplegangers. After you kill them, show the diary to one of the dukes. Sarevok will attack you so have all your characters concentrate on him with ranged weapons while he chases your main character around. After about 15 seconds, a mage will show up and teleport Sarevok out of the room.