Like other monotheists, they believe in something called “God.” But then it gets interesting, as well as confusing, as these people were illiterate from time out of mind, and their revelation has been orally transmitted since. . .no one knows when.
There are seven holy angels, from what I can make out. Melek Taus, the “Peacock Angel,” was assigned by God to watch over his Creation from the beginning. He is not reliable; though I think identifying him with Satan might go too far. The idea of giving obeisance to a cosmic agent known to be crooked and unpredictable strikes me as odd. Sometimes this Peacock Angel is very bad indeed; sometimes, however, he weeps and asks God for forgiveness. But for sure, he retains great worldly Power.
I think (and am no expert, remember) that the Yazidi attitude towards spiritual beings is, “the art of the deal.” Perhaps this view is shared by most pagan religions: “Let us not take sides between good and evil, it might cost us.” Instead, negotiate with whatever comes forward. More.
Reality check: It doesn’t work, as Warren goes n to point out when the devil has turned at last to religion and is in a fanatical mood.
See also: Imagine a world of religions that naturalism might indeed be able to explain (early religion)