Imagine the universe as a cold and uncaring being that sees galaxies as specks of dust, and you begin to imagine Yog-Sothoth. It is the All-in-one, coterminous with all time and space, but somehow locked outside of conventional reality.
Oddly enough, this extradimensional being has birthed children on humans. Then again, there was a wizard involved, which clouds the issue. This might be like saying that plutonium mates with the human body to create a child called cancer.
Yog-Sothoth is normally depicted as a cloud of interlocking spheres. Whether this represents its true form, or whether its true form could be perceived and understood by humans is another question altogether.
Yog-Sothoth is worshipped by those who seek the ultimate answers to the universe, no matter which path they follow. Scientists, alchemists and wizards all seek the knowledge that Yog-Sothoth represents, and sometimes their devotion gets confused.