This is a massive, 50 km. tall megastructure and construct/machine that defends the most vital areas in the universe for the sake of the universe's own survival.
They are practically indestructible and has enough power to unleash a beam of energy that can detonate stars. Usually though, they stay dormant and only activates if a large enough threat arrives.
They can additionally launch swarm of millions of car-sized drones for added defense and offense.
They are often regarded as Gods due to their size, invulnerability and mysterious origin.