http://monergiwmuoskoc43fj6vfbcrll5wjrbl647cdgg2zuwkbu77o7v5vyd.onion/cold-storage/offline-transaction-signing.html
With seed passphrase, you can also create decoy wallets that contain a little bit of money and can protect you from torturers or blackmailers who demand money from you. If you want to create an offline wallet with seed and seed passphrase, create an offline wallet, record the seed on paper, delete the wallet file, generate seed offset passphrase, record seed offset passphrase on paper, and execute monero-wallet-cli --generate-new-wallet /path/to/wallet-file...