Spirit War

With the war on Carnac lost and necron armies marching upon the world spirit, spiritseer Nestra Orphiel summons an army of long-dead Alaitocii to hold the enemy off while the exodites of Carnac evacuate. Kael Ra, the Prince Ecliptic and long-dead hero of the craftworld, takes to a mighty Wraithlord to lead a host of the dead. As the spirit warriors clash with the numberless hordes of the necrons, the final fate of Carnac hangs in the balance.

Read it because
The concluding part of The Carnac Campaign, also available in The Eldar Collection.