Whose vault was 713?
Whose vault was 713? Behind the scenes. It is unknown whom exactly the Vault belongs to but it could be assumed that it belongs to either Hogwarts, Albus Dumbledore or Nicolas Flamel. The vault's number can be separated to have 7 and 13, the two of the most well known lucky (7) and unlucky (13) numbers.
Who killed Griphook?
Later he is killed by Voldemort after the Dark Lord learns of the break-in at Gringotts.
What is the only place safer than Gringotts?
???? Gringotts, the wizard bank! Ain't no safer place. Not one. Except perhaps Hogwarts. ~ Rubeus Hagrid.