I am Selling 114 Dark Pyramids which can be used for the following:

Isolation Bureau
50 Refining Lab Chassis
50 Calming Amplifier
50 Dark Pyramid
100 Energy
Planet Structure - Size:2, All Resources:1, Cloak:200
All bonuses double if built on a planet that only YOU have scanned (limit 1 per planet)

Resonance Inhibitor
50 Dark Pyramids
30 Containment Cages
40 Spy Uplink Chassis
100 Energy
Planet Structure - Size:1, Cloak:250, Invasion Defense:500 (Limit 2 per planet)

They are also used in the Darkness Falls mission to get:
Void Barrier: Planetary Building, size 1, +110 Cloak