Amethyst, Princess of Gemworld#1(1984)

On Amy Winston's 13th birthday, she receives a mysterious amethyst necklace as a present. That night, she is kidnapped by ogres and Lord Sardonyx and taken to Fortress Opal in Gemworld, a magical realm inhabited by people who draw power from gemstones. As she is transported to Gemworld, she transforms into a grown woman. Granch saves her, helps her escape, and takes her to Citrina, Witch-Mother and the Regent Ruler of House Amethyst, for protection. Citrina takes Amy to safety in Castle Amethyst while Granch stays behind to deal with Lord Sardonyx and his death hounds, who were pursuing them. The next morning, Citrina explaines Amy's past to her: she is actually Princess Amethyst, the only daughter of Lord and Lady Amethyst, who were the rightful rulers of Gemworld until they were killed twenty years ago by Dark Opal. Before her birth parents had fallen in battle, they charged Citrina with their infant daughter's protection. She created a rift in time and space and took the infant to Earth, where she was adopted by Herb Winston and Marion Winston and given the name Amy. Citrina and the remainder of House Amethyst, meanwhile, spread the word that Princess Amethyst had died and swore fealty to the new ruler of Gemworld while secretly waiting for the day their Princess would be old enough to assume her rightful throne. Citrina had planned to communicate with Amy through the amethyst necklace she had gifted her for her birthday and introduce her to her true past slowly. Unfortunately, Citrina explains, Dark Opal suspected that Amethyst was not really dead, uncovered where she was, and sent his ogres after Amy, hence her abduction from Earth the night prior. She also explains that time flows differently between the two worlds, so thirteen years for Amy on Earth was twenty years on Gemworld. This time difference would cause Amy to grow older or younger whenever she portals between Gemworld and Earth. Amy, upset, exclaims that she does not want to be Princess Amethyst; she just wants to go home. Citrina agrees, but before they can leave Castle Amethyst is attacked by Sardonyx and the Forces of House Opal. Citrina begins to teach Amy how to wield the power of her gemstone as they fight to protect the castle, as Citrina's own power is not enough to counter Sardonyx's. Amy successfully constructs a defensive dome that pushes the invaders away from the castle, and Sardonyx admits defeat. He returns to Fortress Opal to report his failure to Lord Opal, who is furious. Amy again requests to go home, and Citrina teaches her how to use the power of her gemstone to create a portal back to Earth. While several hours had passed in Gemworld, only a few moments have passed on Earth. But her parents have noticed her absence and are relieved to see her home. Later that night, Amy, still curious about Gemworld, decides she wants to return. Thinking about returning opens a portal, and she steps through to the throne room of Castle Amethyst. But she is not alone.