The Spirit Inferno Domain was extremely large and ruled by the Artifact Inferno Guardian Sect, a second-grade sect.
However, this didn't mean there was only the Artifact Inferno Guardian Sect was the only place that existed; in fact, because of the Spirit Inferno Domain's size, the Artifact Inferno Guardian Sect couldn't oversee everything all at once, especially with their main focus on forging.
So, the Artifact Inferno Guardian Sect naturally had its subordinary first-grade sects (Grand Sects) under it that handled the Spirit Inferno Domain, and then there were elemental-grade sects, which had subordinary powers below the first-grade sects.