The Elder Civil War

The Elders were afraid of a threat from outside the Milky Way. They thought it would still be dangerous to them after they left their physical form.
The entire Milky Way galaxy is surrounded by an artificial Galactic Shield that the Elders constructed. There are dozens of Roach Motels spread throughout the galaxy. Within them, there are devices floating deep within the parent star, that are siphoning off part of the star’s energy. More energy than could be used within that star system. Most of the energy is going into higher spacetime. That energy is used to power the Galactic Shield.
The Wormhole Network is a conduit to funnel energy, from ‘Force Lines’ generated by the super-massive black hole at the center of the galaxy, up into higher spacetime. Those force lines radiate roughly along spirals like the visible arms of the galaxy, although they don’t align exactly. The Wormhole Network originally just used energy from the force lines to power the wormholes, and later the Elders repurposed the Wormhole Network as a power source, rather than build a new energy extraction mechanism. The Wormhole Network wasn’t left active for the convenience of future species.
The Elders did not think there would be any intelligent species in the galaxy after they ascended. Just in case they were wrong about that, and filthy future aliens did arise to roam around the galaxy, the Elders created Sentinels and set Guardians in the Roach Motels to protect the energy-feed devices in the stars there. Most of those star systems are unknown even to the Rindhalu, because they were disguised as ordinary red dwarf systems so dull that no one would bother exploring there. The energy from all those Roach Motels and from the entire Wormhole Network has been and is still going to the energy barrier that wraps around the galaxy like a bubble.
The Elders did not consider themselves to be responsible for protecting the myriad intelligent species currently inhabiting the Milky Way, because they did not think there would be any such beings after they ascended. It was not because the Elders assumed this external threat would ravage the galaxy, wiping out any intelligent life that still had physical form. The energy barrier around the galaxy prevented any external threat from coming through. The Elders assumed there would not be any intelligent life after them, because they ***planned*** for there not to be any future intelligent life in the galaxy.

While the Elders were still contemplating the notion of ascending. One faction wanted to ascend, partly as protection against the threat from beyond the galaxy. The other faction mostly agreed with the plan for ascension, but not with the measures the first faction proposed to secure the future.
The Security faction felt there was only one way to assure future intelligent species did not screw with the vital protection mechanisms they needed to leave behind. That one way was simple: make sure no future intelligent species ever developed. The Security faction planned to leave behind Sentinels to destroy any signs of intelligent life, even things as simple as primitive cities. Nip it in the bud, was their plan. Don’t let filthy aliens develop into a threat, wipe them out before they developed space travel. Wipe them from existence as soon as they developed the ability to use tools, or control fire. That was the plan.
The Balance faction was horrified by the idea of committing genocide over and over and over, just to prevent the vanishingly faint possibility that a future species could interfere with technology far beyond their understanding. If a species rose far enough to attain star travel, the Balance faction proposed that their AIs would reveal themselves and explain why the various Roach Motels and wormholes must not be disturbed, for the benefit of everyone. The Security faction did not see the alternative approach as balance, they saw it as weakness. The resulting war was horrific, it was devastating, and in the end, it was a complete victory for the Security faction.