World Seed

The «World Seed» was given to Kirito after he had saved Asuna from the clutches of Oberon. A computerized memory of Kayaba Akihiko desired that Kirito plant the seed and let it sprout.

Background
«World Seed» is a program that allows the creation of VRMMORPG. It was originally developed by Kayaba Akihiko and was primarily used in the creation of Sword Art Online. It was given to Kirito to decide what to do with it, so he decides to publish it (with Agil's help) on a server so everyone can download it for free. Using the World Seed as a base, cyber technicians can further develop the VR world.

All games using the seed as their game engine allows conversion of one account in a seed-based VR world to another. For example, this ability is used by Kirito when he converts his account from SAO to Gun Gale Online and back.

The seed includes the base programs need to create a VR world, such as the audio and video system, as well as the Cardinal program used in SAO to help in the development of the game which is able to automatically include new quests, NPCs and stories to the games based on myths, legends or stories of the real world. It can create an infinite number of quests, and can even modify entire maps from the game. It is made so the created VR world doesn't require one large server like the original SAO but can run on multiple smaller servers.