Dimension
Yao Wang teleported himself back to the sacred demon dimension through a spell paper given to him by the elder who controlled the teleportation matrices at the sacred demon dimension, after reaching the sacred Demon dimension he was greeted by the Oscar who brought him to the dinning room where the other elders and the two young guardians, Mo Fang and Mo Shen were also there as well.
The Mo brothers as you already know are one of the key members of the clan, their usefulness to the clan was only interior to the clan leader and the great guardian, their ranks are the same as the elders even though they are still young, they aren't even up to eighteen yet.
One can even say that they are important because of their mastering of the ancient spells such as the one to start the purple lightning tribulation that was needed before a clan leader could be made, they also possess the ability to master the spells that can help to access the sacred demon dimension and many more.