The remarkable Serapeum is located on the West Bank of the Nile River about 30 miles from Cairo, Egypt near Saqqara. 
It is an underground labyrinth of tunnels carved out of solid bedrock.
There are caverns that deviate from the tunnels.
In each of these caverns there is a 70 ton granite box with a 20 ton lid on top.
All these giant rectangular shaped containers are carved out of the same granite from approximately 500 miles away in Aswan, Egypt.
They are cut and hollowed out with perfection and polished very smoothly.
The underside of the lid is exactly square with the vertical surface of the inside of the box. So it is perfectly parallel and the lid fits on top precisely.
All these 90 ton granite containers were somehow transported into each niche through the hallways that would barely accommodate the width of them.
A large granite container was found in the Kings Chamber of the Great Pyramid. Smaller granite boxes were found in each of the other two pyramids at Giza. 
These were the precursors to the building of the multiple granite cartons in the Serapeum which are about 4 meters (over 13 ft.) long and 2.5 meters (over 8 ft.) high.
Granite which is exceeded in hardness only by diamonds consists of feldspar, quartz and mica. Cutting granite with diamond power drills would not produce the smoothness that is exhibited.
The inside of these containers have a mirror-like finish. 
With the perfectly fitting lid an air tight vacuum is created.
Provided with power from the pyramids in Saqqara these conductive granular crystalline boxes would produce a piezoelectric effect. The flawless engineering would create insulating properties permitting the ionization of the air.
Resonating vibration and sound would be generated and the transduction of biophotonic healing would be enhanced.
Thus rejuvenation of tissues and amplification of consciousness were obtained through channeling of electrical energy via geometric structures and conductive material.
With the 90 ton boxes fitting tightly into each room of this complex system of tunnels the art of vibration and sound was mastered.
They perfected the resonating of frequencies to such an extent that they could transport consciousness to different realities or dimensions.
They could time travel and ride the waves of cosmic currents. 
What happened to this advanced culture?
Evidence for some sort of catastrophe abounds.
The Step Pyramid at Saqqara looks like it exploded.
the Great Pyramid at Giza has interior areas which are blackened and burnt.
Even far away in Bolivia the exceedingly hard diorite which made up Puma Punku was blown to bits.
Megalithic building projects were abandoned.
Many giant Moai statues on Easter Island were left in the volcano from where they were made.
A 1000 ton block at Baalbek in Lebanon went unused by the temple complex.
A 1200 ton obelisk was left in the quarry at Aswan.
The rock cut city of Petra in Jordan was not finished.
Rock hewn temples in India were not quite completed. 
A granite coffin being transported into the Serapeum was left out front.
There are many more levels of the Serapeum which are kept off limits.
Each level has a series of kilometers long subterranean tunnels impossibly cut out of the bedrock.
Each tunnel has adjoining caverns with precisely carved 90 ton rose granite boxes that were somehow levitated into them.
The official story is that the Serapeum is a burial place for sacred Apis bulls.
The official story of the pyramids is that they are a burial place for pharaohs.
There was a much higher and profound intent involved.
Expansion of the Mind
My best guess as to the fate of these Ascended Masters is that they were infiltrated.
The pyramid system was purposely overloaded.
Maybe many were in the Serapeum sleeping in a state of suspended animation
Most were probably killed by their own advanced energy technology being used as a weapon against them.
But isn’t death just another frequency and sleep another vibration?