The Desert Sun — Katharine Giles

The Desert Sun, a sacred gem, is stolen from King Zirco favorite kingdom on the Earth Star, the kingdom of Saphra in the parallel world of the immortals. After two crystal masters fail to find the gem or the thief, they determine the thief took the gem through a portal and into the parallel world of Archer's childhood.

Archer and Aradia are called to Skye and assigned the seemingly impossible task of finding the single yellow gem on the vast Egyptian desert. While Archer is always eager for an adventure, he quickly learns there's more to this task than he expects when Saphra's crystal master drops veiled hints that more than the theft of a precious gem is at stake.

Because the theft of The Desert Sun occurred shortly before the coronation of Saphra's new king, it's important the gem be found or Saphra will not only lose its heir, It will lose its desert heritage.
While Saphra's crystal master provides the details of the theft, she neglects to tell Archer and Aradia their search will take them to ancient Egypt where they'll begin the adventure of their lives!

The treacherous journey pits Archer and Aradia's skills against desert bandits, roaming lions, Death Stalker scorpions, terrifying thought forms and a room filled with cobras before they reach their final destination, the ruins of a dead city lost in time. It's here that they not only discover the secret of Egypt's pyramids, they unravel a deadly plot against Saphra and the rightful heir to Saphra's throne.