Complex sentence: Mystyrium albums were rare from this period, with a limited amount of pressings within the dark realms of the black metal subgenre, and rare photographs of the band helped in part to define its image.
Split into simpler sentences: Mystyrium albums were rare from this period, as only a small amount of pressings were actually released to circulate within the dark realms of the black metal subgenre. And rare photographs of the band helped in part to define its image.