Shadows of Atlantis - The Golden Age Series, #2

Shadows of Atlantis; Book 2 of the Golden Age Series. DD Adair's sparkling debut Golden Age Series gathers years of research into a rollicking fantasy that is "historically probable", and set in the Golden Age of Atlantis. Step into the intrigue, the crystal technology, and  romance. Witness the metaphysical powers, prolific arts, and mixing of species. Fall in love with archetypal characters as they explore other parts of the ancient world.
Three crystals, two sisters, one impossible choice. Ziel trains Ahna and Aiela to be keepers of the crystals. Learning the maze, weapons, poisons, even combat, is one thing-programming to guard against mind control is quite another. Ahna finds her tribe in the House of Oracles, even as the mega-crystals plague her with disastrous visions. Aiela struggles to keep up with all the training, and her duties in the House of Rulers-then has to rescue Ahna, who's gone off to Belial in search of Carver.
But that's not nearly the worst she'll face. Mardu attacks Greece with his Mutazio: Step two of his plan. Carver plots to thwart his father, because he can't get Ahna out of his heart. Turner captains a fleet of ships, running crystals for Belial, discovering the secret Carver wants kept from the twins.