Zindarak, also known as the Fiery Messenger, is a mysterious fiery entity, which is one of the Great Old Ones that shall release Cthulhu from his prison once the stars are right.
It is believed that Zindarak is a representative of the Fire Vampires, an pyrokinetic race of alien beings that serves one of the Great Old Ones named Fthaggua. Although this is hardly the case. But on the other hand, he is a servant of the Outer God named Ghroth, which flies past the planets in different corners of the universe and as a result of its voice awakens any of the Old Ones nearby. So, Zindarak is likely to working on behalf of his masters.