Each of the guards is part of the whole, without which life would be impossible. They are the nature of this world, the foundation of the world. Some are aware of them, some even deify them, but still most are unaware of their existence, or simply do not think about it. Each of the Sentinels was given a physical shell only after living beings came into existence, so their appearance is close to what exists today. The Star Guardians know each other in the firmament, but few of them are in contact with each other in the rest of the world.
Originally there was only one Starguard, Adam, but with how quickly new worlds evolved, leaving all the laws of nature and world constants in the person of one being was dangerous, as the world is completely unpredictable and could harm itself through Adam. Then the first Sentinels besides Adam appeared - time and matter. The three Guardians were fundamental to all that was at the moment, each carefully stepping into his own world and knowing it. Adam was more than positive about this kind of separation, as it brightened his loneliness over the absence of his own kind.
Later, the rest of the Sentinels appeared, finally dividing all power among themselves.
Star Guards have no right to harm living beings; if a Guardian does so, he is put to sleep indefinitely.