Crux of Darkness
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Cruxes are large polyhedral objects, made of the same chiseled-obsidian material as other artifacts of the Pyramids. They hover in place with their longest point facing down; when activated, their panels open and fragment to reveal an orange-glowing core, and small pieces of their exterior join together to form a Splinter of Darkness. When inactive, their surfaces continually ripple in a wave of small triangular segments. There are two known types of Cruxes. Those that are commonplace are roughly the size of a Fallen Brig, whilst the one inside Riis-Reborn Approach where Eramis preached to her Fallen is nearly the size of a Skiff.
Cruxes may have a role in spying on locations of interest for the Pyramids, as several hover outside of reach in the current Europan Eclipse Zone, the part of the Rathmore Chaos most afflicted by the collapse of the Morning Star at the present moment. They will occasionally teleport short distances when not being observed. The presence of the Cruxes also increases the amount of ambient Darkness in the area, boosting the ability cooldowns of all Stasis subclasses within their vicinity.
Cruxes of Darkness were later used by the Scorn, in conjunction with Pyramid Spikes, to attack The Wellspring in Savathûn's Throne World. Here, they would also demonstrate the power to make the leader of the attack immune to damage, until enough Pyramid Spikes were destroyed, forcing the Crux to disappear.
Official render of the Crux by Ethan Scheu and Aaron Cruz.