Carras is a smuggler working under Saemon Havarian in Amkethran. The first time in Baldur's Gate II Chapter 8 when you enter the Smuggler's Cave in Amkethran, you will see some of Balthazar's monks shutting the smugglers' business down. Regardless of whether you help the smugglers or not, you can trade with Carras, although you can only do it once. If you don't enter the cave in Chapter 8, you will have missed your chance, even if you go in the Smuggler's Cave in Chapter 9.