0xCrystals is an NFT scam where a Twitter account Tweets out the link to a '0.25 ETH surprise mint' that is supposed to be very limited. In reality the mint has been going on since late 2021, originally said it was free, runs fake giveaways, changes Twitter username every few weeks, and uses NFT profile pictures they don't own. The scheme has netted the scammer $1m+.