One on One: Vergen is a side quest featured in the second Witcher 2 Assassins of Kings Enhanced Edition act, if you play the game following Iorveth’s path.
The quest can be completed as soon as you enter Vergen, if you talk to a character named Sheridan.
“The Vergen dwarves liked simple pastimes, and fisting matches were among them. At the time, there was a tournament offering monetary rewards going on at the inn and Geralt decided to win it. Young Zin, would be his first opponent.”
When to start
While playing The War Council
In Vergen, when you enter the inn for the first time, locate Sheridan in the room near the stairs that take you to your room (assuming you follow the dwarf guide named Skalen).
Sheridan will offer additional information about your opponents. First you have to defeat Zin, then Stel Placeholdern. Your last opponent will be Percy Boruk, also known as Percy of Woodham.
Note: If you finished One on One: Flotsam, you already know how a fist fight goes in Witcher 2. You must complete a series of quick-events by pressing the corresponded keys that appear on your screen. When your opponents health bar is depleted you win the match.
Participating in the tournament held in Vergens inn is a good way to increase the amount of Orens you have, as long as you win every match.
After you beat Percy Boruk, a new challenger will appear, named Sir Silgrat, who wishes to fight you. If you decide to fight against him, you will win more Orens; however you can also decline this challenge.