Downfalls of Shuma-Gorath

Shuma-Gorath attempted to reenter the Earth dimension through the weakened Ancient One's mind. The Ancient One ordered Doctor Strange to kill him to prevent Shuma-Gorath's return. With this the Ancient One's physical body died and Strange officially became the next Sorcerer Supreme.

Another time, Nicholas Scratch summoned the demon to Earth to offer his services to Shuma Gorath. It took Doctor Strange, Fantastic Four, Diablo, and Salem's Seven to drive the demon back to his dimension.

Powers

In his dimesion, Shuma Gorath was nearly omnipotent. However while on Earth he wasn't as powerful. He could shape-shift into different sizes and forms as well as become intangible, invisible,or teleport. He has vast manipulation over minds which was one of his tricks with the Ancient One. He can teleport and enter other dimensions or create dimensional barriers. He was nearly invincible, but was vulnerable to the strongest magics. He is magically strong, and his strength level is not yet known. He can also shapeshift, liquify his body, and shoot lasers from his eyes. He also can form energy between his tentacles that is strong enough to wipe out an entire reality. He also has great resistance to damage due to his rubbery form and can use his tentacles as fatal weapons. Being a demon of high order, he can summon hordes of demons to do his bidding. He is very intelligent, probably one of the smartest beings in the universe. He is pushing omniscience.