It is easier to understand the power of unlockables once you have an NFT that has been Darkblock upgraded in your own wallet. So, here is Buddy. He is a Polygon NFT that anyone can claim.
(Quick note on claiming him, even though he is free, your Polygon wallet needs to have some MATIC to cover the tiny gas fee. A new wallet with no MATIC will not be able to claim. We will have a better fix for this soon.)