Avesta! is an abstract game themed loosely on the Zend Avesta - the sacred texts of Zoroaster (also called Zarathustra). It is chess-like in the powers and types of moves available, but there are a few spaces on the board that are limited to certain pieces, some pieces are used for blocking only, and some pieces are promoted when others are captured, which can tip the balance, making a capture or sacrifice critical to the outcome. There are two winning conditions: either the capture of the opponent’s offensive pieces, or the defilement (occupation) of your opponent’s temple for a full turn.

From the flavor text in the instructions:
Many centuries ago, the prophet Zoroaster received a revelation of Ahura Mazda, the God of Light, and Ahriman, the God of darkness. This gnosis of the eternal struggles between the holy and the evil spread across the ancient Persian Empire through the pages of the sacred text called… Avesta. This is an abstract strategy game themed loosely on the Zend-I-Avesta - the sacred texts of Zoroaster (also called Zarathustra).
The pieces reflect spiritual powers struggling for victory: the Spirit, High Priest, Preceptors, Acolytes, and Varzas. The board includes spaces with significance during play: the Altars, Temples, and the Vortex at the center.
It is chess-like in the powers and types of moves available, but there are a few spaces on the board that are limited to certain pieces, some pieces are used for blocking only, and promotions may be used to your advantage.