The Sixth Dimension serves as a 'Multiversal Control Room' which stands at the very top of the Multiversal scale.
The Sixth Dimension is a godlike dimension and the highest plane of existence and exists beyond imagination and time. This is the realm of things beyond the imagination; where the Multiverse was designed and set in motion. Perpetua, the progenitor of Totality and her three sons: the World Forger, the Anti-Monitor, and the Over-Monitor are the only beings known to reside within the Sixth Dimension.
If, by some extreme circumstance, any of the four residents are destroyed, they reform in the Sixth Dimension. It is almost impossible to gain access to the Sixth Dimension unless the Multiverse is in jeopardy like the Source Wall breaks. Mister Mxyzptlk, a creature from the Fifth Dimension, was only able to open a portal when the Source Wall, the boundaries of reality, had been broken, an act that took a large chunk of his energy. The happenings of the Sixth Dimension were completely beyond the perception of Mister Mxyzptlk's energy.