A multisig wallet locks coins to several keys and a threshold. The most common setup is 2 of 3: three keys exist, any two can sign. One key lost is not a disaster; one key stolen is not enough.
Spread the keys
- Keep each key on a different device, ideally from different makers.
- Store them in different places: home, a safe deposit box, a trusted person.
- No single fire, theft or mistake should reach two keys at once.
The part people forget
To rebuild a multisig wallet, two seed phrases are not enough on their own. You also need the wallet's description: the list of all three public keys and the threshold, often saved as an output descriptor or a wallet backup file. Keep a copy of it with each key. It cannot spend anything, but without it, recovery can become very hard.