The Spires are terraformed structures created by a race of Ancients. The Spires destroy every living thing within range of their pulse wave.
There are 7 spires in the Milky Way Galaxy. A group of religiously fanatic Shraadus are to believe that these spires somehow relate to the false deity named "Echidna".
One of our Galaxy's Spires, preparing to fire
An image of the Spire's range.
The ancients who built these weapons did not build them to be weapons in the beginning. They were actually built as tools to create the building blocks of life across thousands of planets within this galaxy to create the life we know today. These weapons work by sending out intense energy waves designed to work on "frequencies" that target specific things such as organic matter and either break them down to their specific atoms, or to reconfigure these atoms into the building blocks of life. Some frequencies are locked out of the system though, because if they fired on these frequencies it would destroy the structure themselves as well as nearby planets within their range.
These spires are defended by a small garrison of robots and by one of the eight remaining judicators.