The Silver Vortex. Guardians of the Tall Stones, #4

The Silver Vortex is the final book of the Guardians of the Tall Stones series. From beyond time and space they come to walk the earth once more: the Guardians of the Tall Stones, the Lords of the Sun... Deva is the beautiful and headstrong daughter of the High Priest of the greatest of the mighty stone circles. She seeks to master the arts of sorcery in order to reclaim her lover from a previous incarnation.
Now, trapped by a desire she cannot control, she risks more than herself, and puts the whole community in danger... In an adventure of Bronze Age Britain and 18th dynasty Egypt, ancient jealousies, hatreds and passions emerge to confront each other on the great journey to the higher realms.