Dragon eggs

Dragon Eggs are -logically- the eggs from which Dragons hatch. This fact alone should be warning enough to not mess around with them, as the adult Dragons won't take kindly to someone messing around with their offsprings.

In Ultima VI, the Avatar had to get a Dragon Egg from the dungeon Destard, before Sandy in Trinsic would reveal the remaining Ten Pirates of Hawkins to the Avatar. Any surplus eggs were given to Shubin at Serpent's Hold, who wanted to turn them into a special meal. Dragon Eggs were again seen in Destard in Ultima IX. However, by then they were so big that the Avatar couldn't carry them, and only managed to get some parts of the shells.