Loot the key off his body and open a nearby cupboard. Just watch as Roche gruesomely exacts his revenge.

Thankfully, Geralt and Roche will enter the area. Head over down there, only to find Dethmold indulging in homosexual acts. He's busy doing something in the ruined library ( #5). After you kill him, the next in the line is Dethmold. He's your classical mage opponent with teleport, fireballs, lightning bolts and absorbing shields. After defeating all the incoming soldiers, move on with Roche to the area with #4.ДЄfter several soldiers in that area's you'll battle Dethmold's apprentice. You'll also notice Dethmold's apprentice issuing orders around. The area at #3 will feature a lengthy fight. There's really only one way you can go, so just follow the way from where the incoming soldiers arrive. Roche will then tell you that he'll go by the walls while you take the ground. Traverse to the otherside of the tunnel ( #2) and you'll witness some amazing teamwork from Roche and Geralt. Using Axii signs, you'll charm them and they'll be an easy prey for you and Roche. The quest starts by talking to Roche at #1, in front of the sewers whose entrance is guarded by two kaedweni soldiers. Anais, the only heir to the Temerian throne with royal blood, is in Dethmold's hands in Kaedweni camp. It's mutually exclusive with Where is Triss Merigold?. If during For Temeria! you opt to go with Roche and save Anais, you'll receive this quest.

The witcher 2 royal blood