The Final Void War
War in space is so cool that we decide to do a lot of it until we no longer think it is cool and we make it illegal.
When The Volagog moved into detectable range of whoever it sparked a holy war within The Cult of Eternal Iron which spills out of the cult into mainstream Dwarven religious institutions and then spills out further until largely everyone is caught up in the mess. Because interstellar trade was heavily tied to guild politics, and guild politics were tied to the allegiances of certain houses it didn't take much for a serious religious dispute to snowball into a war on a scale not seen since the Ethnostate Wars.
With much greater access to rapid interstellar transportation the pace of void warfare was much faster than previous wars and even without manifested gods the destructive power unleashed during this war was almost unthinkable. An armada riding on the laser canals could scorch clean hundreds of worlds without even needing to slow down, disks and stars could be flung like bullets at other disks, and at least one black hole was detonated in the middle of a system of disks. The weapons of this war were great in their destructive power, but they left nothing behind. What good was conquering your neighbor when to do it your neighbor was scoured from the face of the universe? What good was taking territory anyway when the guilds were more than capable of dragging new worlds to you from the far reaches of space?
Eventually the fighting stopped as those involved either ran out of people to send to war or were overthrown by a populace that would not allow further killing. All surviving polities agreed unanimously to ban all void warfare, resolving that any military conflict between nations could only be solved in atmosphere. Failure to do so would result in complete detachment from the bi-frost and a dismantling of all guild infrastructure. If you would fight amongst the stars then you would be denied travel amongst them.
The ultimate result of the war was the massive empowering of local Forge Monasteries. The guilds, for all their connections and power still relied on the work of their Forgeborne members to operate, and they relied on recruitment from Forges to grow that membership.