Item from Sword Art Online by Reki Kawahara
Kayaba's final gift — an open-source package for building virtual worlds, left behind by a mass murderer who wanted his dream to outlive his crime.
The Seed is Kayaba's legacy and the most morally complicated gift in the series. It's an open-source toolkit that allows anyone to create full-dive VR worlds using the same Cardinal System engine that powered SAO. After Kirito released it publicly, it spawned hundreds of virtual worlds — ALO, GGO, and countless others all run on Seed-based technology. Kayaba gave it to Kirito specifically because he trusted Kirito to release it rather than destroy it. He was betting that the technology was more important than the crime — that virtual worlds would become essential to human civilization, and that his death game was the birth pain of something greater. Whether he was right is the series' central unresolved question.
The Seed has no physical form — it's a software package, a small program contained in a virtual teardrop of light that Kayaba's ghost gave to Kirito. When activated, it unfolds into the complete development framework for creating Cardinal System-based virtual worlds.
Also known as: The Seed, The World Seed