The Cosmic Battle
Good and evil are engaged in a cosmic struggle with an assured outcome.
The forces of truth (Ahura Mazda) and the forces of the lie (Angra Mainyu) are engaged in cosmic battle. But this is not eternal dualism - good is assured victory. The battle has a beginning and will have an end.
Truth shall overcome the Lie at the last.
The assured victory of good makes this ethical rather than metaphysical dualism.
Eschatology