The Moon Altar will provide you with access to golden NFTs. This upgrade will give your cards a unique visual look in battle. They will be much rarer and more limited than normal NFTs and will retain a much higher collectible value. With them you will be able to access thematic tournaments, and they will allow you to use the NFT staking function.
To get a golden NFT you will have to collect a certain number of NFTs of the same copy and perform a burning method with them. By burning the NFTs, you will obtain a copy of the same NFT but with a golden frame