As some of you may know, Satanism is definitely compatible with Hinduism. Anton LaVey even linked Satan to Shiva. Shiva is, in Hinduism, one of the 3 cosmic functions and persons of the Hindu Trinity also known as the Trimūrti; Brahma, the creator, Vishnu, the maintainer or preserver and Shiva, the destroyer or transformer.
Ishvara, which means “Lord”, is the Supreme Being, the Supreme Cosmic Being, in Hinduism. The term “God” does apply to Ishvara as well as the Trimūrti. Therefore, a Theistic Satanist can definitely believe in God. An Atheistic Satanist could always see God as the ultimate cosmic energy in the universe. The term “God” with a capital G, despite popular belief, is not exclusively Judeo-Christian or Abrahamic.