Also that the void between stars is safe
Still not sure that's true. Yes, the Gysian told us that, and he might even believe it, but he could have been lied to or not know himself. The issues are twofold, and both come down to the inability to do proper interstellar light cone forensics:
The first issue is that all this stellar-scale construction and war ought to have been noticed by human astronomers and hadn't been for some reason. The galaxy is, after all, "only" 100,000 light years across, so humanity ought to be seeing the results of the occasional Lumen or whatever having been deployed by a hyper-aggressive Shiplord Authority over the centuries, as well as the apparent
terraforming of the entire Galactic Core, the entire thing going dark as it's covered in Dyson Spheres, which ought to terrify everyone exactly as much as it sounds like. Somehow, though, the stars still looked lonely and inviting, for all of human history, when they really,
really shouldn't have; someone, or more likely some
thing, has been carefully wallpapering over all of this, and has been doing it for as long as the stars have been a warzone.
The second issue,
which I brought up way back during the Second Battle of Sol (wow was that really five years ago?), is that the Shiplords themselves don't do light cone forensics on target species, like for instance humanity, even when they desperately want more intel, such as against the Nileans or humanity after the Second Battle of Sol. The final form of Shiplord surveillance, something that even Practice bullshit would have difficulty stopping, would be to use FTL-equipped optical telescopes to gaze "back in time", by just jumping back far enough away to see the light that's still traveling away. The moment that the Tribute Fleet didn't report back, for example, the Shiplords should have been able to jump FTL telescope arrays a few light-days away from Sol and been able to catch a livestream of exactly what went down, but they didn't*, either because they couldn't or because if they tried there'd be something out there waiting for them, something even the Shiplords don't want to mess with, if they tried it.
*- Note that they could have also just set up a listening post at the nearest star, Alpha Centauri, 4.3 light years away and done the same thing, so there's actually even
more complications here.
Point is there's something really weird here, and until that gets cleared up I don't trust that it is actually safe to linger between stars.