Poisoned harpy claw

You can find a small quantity of these on The Blue Stripes' ship, during Chapter II (to reach the ship -it's off the map- you need to approach the boat by the beach next to Roche's camp and use it to travel to the ship) AND on a corpse found just before the inner entrance to the Mines of Vergen. (Right at the point Zoltan makes a comment about the "poor bastard") a