By monitoring gravitational waves, the Successors learned that the galactic core's mass was rapidly decreasing.
Gravity was directly related to mass. As long as a mass was in motion, it would inevitably emit gravitational waves. The greater the mass, the stronger the gravitational waves; the faster it moved, the stronger those waves became as well.
The galactic core possessed both factors. Its gravitational waves were undoubtedly extremely strong and obvious, so observing them was not particularly difficult. The sharp drop in gravitational-wave intensity also meant the Successors' strategy was working: the galactic core's mass had been severely reduced by the large amounts of falling negative mass.
However, because gravitational waves could only travel at the speed of light, the Successors did not learn of this until several years later. The "short distance" between the shield and the galactic core was only short on a cosmic scale.
Proxima Centauri was not particularly far from the Solar System either—only a few light-years away. Yet even light needed years to cover that distance.
During the period before they received the gravitational-wave data, the supergiant-mass organisms were repeatedly attacked by the Exotic Star Hubs. Their method of attacking the supergiant-mass organisms was the same as the Successors': they sent over a black hole bomb.
This caused several supergiant-mass organisms to collapse directly into black holes.
The Successors found interception and defense extremely difficult. To the enemy, supergiant-mass organisms were far too enormous in both volume and mass. Targets of that scale were practically sitting ducks. With bodies on the scale of stellar systems, sniping them from a light-year away was no different from firing point-blank.
However, the Correction Mechanism soon realized that what the Exotic Star Hubs were doing was meaningless. The supergiant-mass organisms died from black hole collapse, but the mass of their