They used to think life was inevitable, the apex of a beautiful thermodynamic spiral that shaped stone, water, heat, and light into primitive creeper-clays, which blossomed into fantastic shapes as evolution took hold. Again and again, they came to a new world in a likely orbit and saw alien but uncannily familiar forms: smoking chimneys on the ocean floor, continents rolling with rainbow waves—even, once in a very long while, the glint of mirrors pointed at the stars. Their best geological models assured them that wherever the right ingredients met in the right proportions, life would flourish.
They were wrong.
As they sailed further into the cosmos, they realized with growing horror that evolution on rocky planets runs at the edge of a lethal instability. Life branches out in just the wrong way, a new kind of chemistry falls into place, and evolution's kill switch snaps shut, flooding the atmosphere with toxic gas. They found planets with air so corrosive that even their probes succumbed, dug up fossils that could only be handled through layers of glass. They learned it could happen at any time, without warning. 978
It happened on their birthworld, and would have made their home a necropolis, if by that time they hadn't learned enough to stop it. They learned of it, in part, from hundreds of young civilizations that had taken notes—panicked, or meticulous, or sublime—as their planets burned to ash.
They decided to do something about it.
They hurled into space an armada of uncrewed container ships, sailing the slow road to barely-visible stars. Each one was inscribed, in dozens of subideographic hyperlanguages, with an explanation of its purpose. Where they landed, their senders hoped, perplexed scholars or shamans or hive-dancers would eventually read and understand the omens of the disaster the inscriptions foretold. If the need arose, they would open the containers and wake the equipment inside. Armed with magical tools, on a quest as nonsensical as the sickness overcoming them, they would follow the poison in their air to its source and cut the photochemical chains dragging their world to the grave. 514