Bip39 Validator 1 illustration of manually creating entropy could be flipping a coin. But if an attacker will give you a coin that is definitely weighted marginally in favor of heads, your initial supply of entropy may have been corrupted. Generally download / invest in wallets from official Site. Verify https://webookmarks.com/story4049070/bip39-passphrase-optional-seed-phrase-generator-no-further-a-mystery