Shadow Chamber (XCOM2)
The Shadow Chamber is a special research lab for the highest priority and most complex subjects: research that advances the plot is completed here, such as analysing the Blacksite Vial captured at the Blacksite raid and the Codex Brain recovered from the Codex.
Other than its research purposes, it also has a function similar to the Hyperwave Relay. Once built, the composition and total number of the enemies will be revealed on the Geoscape, which will allow XCOM to plan for encounters with particularly powerful enemies. It has no slot to benefit from a staffed Engineer.