Kondar

Named after its original owner, Kondar is an enchanted bastard sword that is more powerful when used against shapeshifters (including doppelgangers), as well as growing warm in their presence. Its normal enhancement bonus is +1, the greater one against shapeshifters +3. It's carried by Aldeth Sashenstar in the game Baldur's Gate, and can be acquired from him by killing him in Cloakwood where he is first encountered, or by helping him there and later also helping him root out the doppelgangers infesting the Seven Suns, whereupon he will give it as a reward. Its property of growing warm in the presence of its prey is not implemented in the game in any way.

The same item also appears in Baldur's Gate II, becoming something of a generic rather than specific item even though it has the same description.