Bip39 Seed. At first you need to store it SEPARATELY out of your seed. Having your seed as well as your passphrase in precisely the same place defeats the purpose of getting a passphrase in the first place. This functions since BIP39 is supported by a lot of wallet makers. https://privatebookmark.com/story19560973/bip39-wallet-https-linktr-ee-bip39-the-fact-about-bip-39-that-no-one-is-suggesting