Silence Please
Go to the end of the beach at Oakvale where you will find a cave. Upon entering the cave the quest will begin. Your first task requires you to sneak pass three bandits and enter the gate. Take note that if your spotted by any of the bandits the gate will close and they will all attack you.If this happens just proceed to kill all of them and stay out of sight of the gate for some time for the gate to re-open accompanied by bandit replacements. (note: for the less sneaky heros, you can also try and kill the bandits with your bow in one shot, either with a master bow or a skilled headshot.)
Long Path Ahead
After bypassing the gate you will overhear two bandits talking about how Twinblade will allow only those in full bandit uniform to enter the camp. After their little chat they will take notice of your presence so prepare your arsenal to confront them. You are required to find ALL pieces of the bandit uniform along the way.There will be numerous bandits here so be careful. At the end of the path there will also be a Demon Door.
First Camp
If you've got a full bandit uniform you will have no trouble by bypassing the first guard. However the next camp needs you to obtain a camp pass. There are several ways to get this pass.By beating a matching game or simply buying one from a bandit at a pricey 1000 gold. You can, as an alternative kill either one of them when no one is looking though this is a more evil choice. Exploring the camp for hidden goods is advisable.
One Step Further
Here there will be one final guard between you and Twinblade. This final obstacle needs you to create a distraction. There are three ways, the first is to free the hostages by killing the bandit guarding them. The second way is to hire the group of assassins to create a diversion for you. And the third is by simply running around the camp and slaugher ewry bandit you see (although this will attract the attention of the bandit guards and will occure with them trying to slaugher you.)
Big surprise
As soon as you enter the new area it appears that Twinblade has been expecting you. Don't be intimidated by his big size, just keep doging his attacks and beware not to stray too near to the bandits as they will attack you. When Twinbalde has his swords stuck in the ground whack him in the back to drain his health. Just keep repeating this process until his health drops to a low level. Here is when the Seeress reveals hereself to be your sister. After the cutscene you will be givn a choice to kill Twinblade or to spare him. Choose wisely