The first wormhole was discovered mindlessly looping in an endless circle a few hundred kilometers beneath a dead rock of a planet. The planet itself played host to a variety of machines, all of infinite age and esoteric functions, and seemed to be what powered the wormhole. Everyone agreed, however, that these machines were definitely not made by human hands.

Growth was exponential after that. By travelling through that first wormhole, a colonizable system was discovered with two wormholes, each with the same incomprehensible machinery. Wormhole after wormhole was discovered, and humanity began to achieve the dreams of the science-fiction writers of past centuries. Freighters plied the shipping lanes while jet-black military ships hunted down pirates and pleasure cruises orbited beautiful gas giants. There was a flurry of excitement when a short burst of transmission was picked up emanating from a wormhole, but its undecipherable nature soon led society to conclude that it was nothing more than another Wow! signal. Colonists from the wearied cities of Earth left in droves, seeking a new life in the frontiers. Intrepid exploration teams landed on planet after planet, asteroid after asteroid, continually pushing the bounds of the Perimeter further into the unknown.

Then the Others came. They poured through wormhole after wormhole, ignoring any ship and planet that tried to surrender and heading doggedly towards Earth. The largest collections of human military might were swept away without much effort, and the time came when their jagged ships infested the prime system of Humanity and hung in geosynchronous orbit around Earth. They deployed a satellite that beamed the same transmission continually. While Earth trembled and prayed for deliverance, the Others did nothing except deploy more satellites with the same message. Scientists began to examine the code until that one terrible day when what was being said was finally realized.
“This is a reminder that your bill is as of yet unpaid to Wormholes Incorporated. To ensure continued use of the wormhole system before your first-contact extension expires, please immediately present the bill to the representatives currently in orbit around your planet. Thank you for travelling Wormholes Incorporated.”
The inconclusive signal from centuries before was decoded rather quickly.
“We hope you have enjoyed your usage of wormholes as provided by Wormholes Incorporated. Your bill is as follows: Forty-six thousand tons of refined gold, twenty planets, and thirty-five thousand medium length asteroids. As our records show you to be a first-time customer, the first-contact clause has been activated and a leeway of a sixth of a galactic orbit. Representatives will arrive upon expiration of the clause and collect the bill. Any sign of resistance will be blasted aside. Thank you for using our wormholes.”