It depends mostly on Your idea. Will Your rogue be a scout type ? Or rather hitman ? For hitman I reccomend good ol' Assassin or, if You like it exotic, Crescent Ninja. Drunken Master should be in Your thoughts too, because many of abilities of this funny class could help Your Duegar surviwe to another day. I doubt that Drow would heal him without gold, and with it ... why shouldn't take it from his screaming body anyway ?

For scout type ... Deepwood Sniper or Acrobat Thief ... or just plain Rogue. Not many other people are as good as them at sneaking. If You are willing to make Your PC more menacing choose Assassin, with plenthora of spells and abilities well equipped Assassin could take out even higer level threats.
My build, if I were going into hitman mode would be along this line.
If stats availble to choose/buy for points. Raise as cheaply as possible as many stats as You have, standard would be about 14 in every stat with point build. Why ? Because racial bonuses will raise important stats even more ... don't remember wich one in case of Duegar. And such high stast will make avaible a lot of feats in the future.
Feats: 1 lvl, "Improved Initiative", 3 lvl "Arterial Strike". Strike first, and make them bleed to death.
I would suggest Weapon Focus in stabbing dagger, and later Improved Critical in this weapon. It is dagger ... and have Critical Threat 18-20. Good option for all assassins worth their salt. And find nice magician who will enchant this trinket with "Wounding" magical ability ... and we are merry.

I would suggest following Rogue path until you reach 10 lvl and take "Crippling Strike" special ability. Nice adition to Your arsenal and completly nonmagical !
Learn to brew poisons, "Craft: Alchemy" is Your friend along with nice DM who give You some recipes. If You would lie to went into poison killer, take deadliest known to You poison that could work as gas ... and feat "Poison Immunity" just to feel safe.
And looking on poisons, deadliest one is not this that is causing greatest damage. Och, no. WHat if this warrior will take 15 Con damage, if he will tear You apart before dying ? Paralyzing or Sleep poisons leave enemy hapless against Your Coup of Grace, wich with Sneak Attack is almost irressistible even for Warrior from 34 lvl, not to mention pathetic opponents that will have to make this Fortitude Save against DC on 5 lvl it might be 24, or more if Your pet Rogue have high Str. On 20 lvl DC reaches insane height of 66 even without magical backups. Rogue is deadliest, because he have to think befor making is move.
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