Timeless Changes — Regan Black

Diana Walsh, descended of an Avalon priestess, has inherited a treasured piece of amber and the repsonsibility of keeping it safe for Sir Kay, its rightful owner. She's studied the history with an eye to the future so she can support and assist Sir Kay, should he return in her lifetime in the 21st century. Since making a vow to King Arthur during his first life in the sixth century, Sir Kay has been chasing his nemesis Mordred through time. When he wakes in a strange new world, he knows the evil sorcerer is making another attempt to restore a powerful immortality talisman. In his pursuit of Mordred, he discovers an unexpected ally in Diana. Knowing there is no hope for humanity if Mordred succeeds, Diana and Kay must unravel a wealth of long-buried secrets and magics before evil grows out of control.