The Operator is a Demon from Zark and thus far the most powerful such individual from there so far. He is immensely powerful, likely to be even stronger than the Woman of Mystery. It is implied that the Operator is/was of much higher social rank than either the Woman of Mystey or Edgar and Chauncy.
Luckily for the rest of the world, the Operator is imprisioned in the Elevator. He is unable to leave, even through the opened doors. Considering the lack of facilities, it appears that the Operator does not have biological neccessities like eating.
Of course, he is still a danger to anyone entering the Elevator. He does not wish to remain confined and has been trying to leave his prison. He has the ability to mentally dominate people coming in, which makes him an extremely high threat.
Due to the above fact, it begs the question of sanity as to why the Operator's cage was made into an elevator and him its elevator-operator.