"A memory manipulation spell has to be cast. The memory is removed and stored inside the crystal. They can be restored later. Memory crystals are very popular with rock trolls and with the Snow Queen." Cora answered. "We have a very special tree, the tree of wisdom. It can answer any question, but only if asked by two people with valiant hearts. Do you have to be valiant to connect to your trees? We have enchanted trees too. They provide enchanted wood."