Sword of Kaer Morhen is a silver sword in The Witcher 2: Assassins of Kings.
It can be found on a skeleton lying between the two rocky outcrops directly south of the ledge you jump down from in order to start the fight against the arachas (in Iorveth's hideout, in the forest outside of Flotsam). It can also be found in the remains of the arachas.