The Key with the Curse — George W.J. Laidlaw

Finding a key leads two brothers into finding a cave that holds a terrible secret. Within the hidden chambers lies a golden sarcophagus. In the coffin is an insane pharaoh suspended in sleep for centuries and who is waiting for his trusted follower to insert the special necklace that will awaken him. If he regains his powers then the world will be lost and it is up to Andrew and Michael and their friends to find a way to prevent it from happening.