The Moon-Eyed Mummy, who appeared in the episode "Mummy Dearest", was a mummy that rested in a tomb that an Egyptian pyramid was built over -- a pyramid that was near the one that the cat pharaoh Azra had a team of slaves building. He wore a ruby pendant that belonged to him, which, if it were taken from him, would cause him to arise from his slumber and journey across Egypt until he found it again. He seems to have the ability to project powerful and painful lightning bolts from his hands.
The Moon-Eyed Mummy was awakened when Azra's head servant Gargotec stole the mummy's pendant in order to gain favor with the finicky cat pharaoh, causing him to go forth from his tomb in order to find the missing pendant. Soon, the mummy finds it around Azra's neck, who then wriggles it off him before he, Gargotec, and Scrupses are chased into the desert by the mummy. Later, the mummy reappears when Brainy places the pendant around his own neck, chasing him around until Brainy was directed to go into the mummy's tomb to lure the mummy back there. Brainy tried to race back out, but his bandaged wrapping got caught by the mummy as he used it to try dragging Brainy into the tomb with him. Grandpa Smurf used a pair of scissors to "cut Brainy's ties to Mummy", which catapulted Brainy out of the tomb while causing the pendant to fly back into the tomb before the other Smurfs sealed it shut.