Know Your Ghost is a method to verify a wallet address that has interacted with a contract/s before a certain block date, this prevents whales from buying all the portals once the first haunt is launched and also stops them from spinning out new addresses to get past other security measures. It also keeps the owner of the wallet private so no KYC required.
This is to allow long term followers of the project, and active community members, from missing out on Aavegotchi from the each generations haunt by giving them access to a portion of the portals through KYG before the portals are available to be bought without limit.
It would be capped at 10 portals per GHST fren that has completed KYG before the main launch with more being able to be purchased after a certain time when it becomes available to everyone.