The Soul of Time - The Time for Alexander Series

Ashley and Alexander come face to face with Volterix, the terrifying Thief of Souls - a druid with powers to stop time and change the future of the world. His army is a group of fanatics called the Eaters of the Dead. Ashley and Alexander must travel to the far north in order to stop the Volterix from irrevocably changing time. With Alexander's soul, and Paul as his puppet, the druid hopes he can stop the Roman legions from conquering Europe and thus save the druids from extinction.
But Ashley knows that will not happen without the mysterious Time-Senders erasing all their lives. In order to save herself, her children, and the men she loves, she has to somehow get Alexander's soul back and find the druid's lair.