Hastur is the Great Old One of The Himalayan Mountains and Outer Tibet, and has placed under his protection the dream-haunted Plateau of Leng. He discovers those who stray too far from their bodies while in a dreaming state, and return them to their slumbers for another 10 years.
Hastur is part of a race of beings known as “the Great Ones.” They are immensely powerful beings that have existed since before time was born. They can take different forms; some look like man or animals and others simply appear as vibrations or colors without any shape at all. They often represent dualities such as joy and sorrow or life and death (though this applies more to younger gods than to the Great Ones, who are beyond such concerns).
Hastur is known as the “King in Yellow.” He appears as an extremely thin man draped in a tattered yellow cloak. His face is concealed by a mask, and his hands wield the Staff of Hastur (also called the Yellow Sign).