Bip39-Master Just one example of manually generating entropy would be flipping a coin. But when an attacker will give you a coin which is weighted slightly in favor of heads, your First source of entropy will have been corrupted. This will produce a bundle that only has the chinese_simplified wordlist, https://seolistlinks.com/story19922779/bip39-word-generator-the-definitive-guide-to-bip39-phrase