The owner, and possible creator, of the Gravity Engine is Yeti of Master Payne's Circus of Adventure. A fair surmise might be made that due to Yeti's size and build, and the name of the invention, the wielder of the Engine needs to be quite sturdy him or herself. The only time the Gravity Engine has been seen in operation so far was [ in preparation to fight] [[Chronology - Volume #|✣ ]] the Monster Horse Beastie in the Circus's camp while Agatha was still travelling with them.