RuneMate Vault is a security feature which protects your OSRS account details behind a secondary PIN or password, so if somebody gains unauthorized access to your RuneMate account, they will not be able to gain access to your OSRS account details.
Initially, all of your accounts will automatically be encrypted with a random password., You can change this password by clicking the padlock ( ) button in the accounts side panel., You can opt to have RuneMate remember this password on this device, so you don't need to enter it every time.