Crystal of Duplicity

Crystal of Duplicity is a crystal which Nystul used to copy the land in Felucca onto Trammel. Minax also used it to be in both Felucca and Trammel. Lord British took from Minax when she infiltrated Trammel. According to Ricardo's research that has been revealed during the In the Shadow of Virtue - Lost and Found Part 3 quest, the crystal is inside Castle Britannia near the throne room. Sherry the Mouse found the crystal at that spot in the begining of the In the Shadow of Virtue event cycle.