Arabian Adventures for DF

[Bira]

This seems to be an Ars Magica-inspired setting as well. That's where the concept of Dominion comes from. Ars Magica games are mostly about magicians belonging to the Hermetic Order, which teaches a "scientific" approach to magic and views magic itself as a morally neutral natural force.

It mostly takes place in a mythic version Europe circa 1220 AD, though campaigns can span many years. As you might expect, the Catholic Church is quite powerful in the areas described by the game, and it mostly disagrees with the Hermetic view of magic. Nevertheless, they are a bit more tolerant of it than it would seem at first glance, in that their first reaction to learning a bunch of wizards set up shop near town isn't to call a crusade down on them. It is, in fact, quite possible to be both a Hermetic magician and a Christian, at least according to the game's mechanics. I suspect the same attitude has been transplanted to this Arabian Nights-style setting, replacing Catholicism with Islam.

Ars Magica has a fine-grained system for mystical auras/power sources. There are several types (Magical, Faerie, Infernal, Dominion), which can have different numerical ratings, and interact with each other in different ways. Dominion is the power of God (who is real in the setting). It's usually strongest in towns and cities with significant churches and/or cathedrals, though you could have a holy place out in the wilderness. It penalizes all the other power sources and enhances powers which call on the divine. "Dominion rises during the calls to prayer" is a perfectly valid interpretation using that framework.

Hermetic magicians, by default, benefit fully from Magical auras (which are neutral), and to a lesser degree from Faerie auras. An Ars wizard could become a diabolist and benefit from Infernal auras, but that's villain material. And an old edition used to have a supplement about Pious Magi who could benefit from Dominion, but I understand they were considered grossly overpowered.