I have a Wand of Lightning, a Red Potion and a Violet Potion in my inventory, but I can't sell any of them in Nashkel or in Carnival. I believe I sold the potions in my last run. Could my problem be caused by my low reputation (8)? EDIT: Eh, sorry. I just sold the potions in another tent that I missed. But I still can't sell the wand. So I'll rephrase my question: are there any simple rules to this? What makes some things vendible in some place and invendible and not vendible in others?