The Spire

 was a 300 kilometer high artifact 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 future. This was used to create tachyonic dark matter (unintentionally making quasars), and delaying the universe's end. Planet-killers sent back in time destroy the Spire after its creation, thus making its very existence a paradox. (PROSE: Ghost Devices)