The Speculum Umbrae is an intricate crystalline device only the size of a human hand that has been formed out of layer upon layer of circuitry that has been arranged like the petals of a flower. It is an ancient piece of archeotech used by the Hereteks of the Empyric Engineers faction of the Dark Mechanicus in the Calixis Sector and, if its staggering demand for power is met, it enables the user to summon the shades of the dead from the Warp and give their energy substance in the mortal realm for a short period of time. This is not an easy task and the device can require the power output of a manufactorum's plasma generator or even an orbital bulk-lifter spacecraft's fusion enginarium before it will function. Most people within the worlds of the Calixis Sector and the broader Imperium of M