Fall of Eidel

The Fall of Eidel marked the end of the Eidellian Empire, with the fall of the Tower of Eidel, the maiming of Tane and Nemeon, and the commencement of their eternal enmity.
Described in the final chapter of the Taneion, the Eldari were besieged by the hordes of Dulicta.  The relationship between Tane and Nemeon had deteriorated to the point that Nemeon withheld the support of his mages from the fight. The final result was the levelling of the ancient city and its divine tower.