You may be looking for the Shadow Spire.
The Spire was a 300 kilometre high artefact on Canopus IV. It was the largest planet-bound structure in human-explored space, and one of the 700 Wonders of the Universe. It was made of futurite, and had a column of tachyons at its core. Those close to it received visions of the future. This was a side-effect, as it was built by the Vo'lach to get matter from the end of the universe from many possible futures. This was used to create tachyonic dark matter (unintentionally making quasars), which delayed the universe's end. Planet-killers were sent back in time to destroy the Spire after its creation, thus making its very existence a paradox. (PROSE: Ghost Devices)
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