Mercenary Gondwin is an associate of Mercenary Humbold. The first time you meet him, together with Humbold, is in Avestrue, on the road from the Old Customs Tower into town. At that time he is too busy chewing to talk to you. The two mercenaries are on their way to knight Traldar of the Silver Falls, who is just recruiting people to help fight the Orc threat on his lands.
Later, outside of Grimtooth Castle, you meet Gondwin again and you have to free him out of the hands of the Orcs. When you do, he shows you the hidden path into the castle.
When you meet Malgorra and if you don't give her the Eye of the Dragon, she kills him.