The Vault of Missing Men
The Vault of Missing Men is a secret vault that only the Phantom and relatives can know off and visit. It is guarded by a big wooden heavy door and locked by a big old fashion lock. The current Phantom has the key. Each vault is either initialed with the persons name or has the Phantoms number that buried him there.
Of current people alive only The Phantom, Diana, Kit, Heloise and Rex have been in there.
Check the PhantomWiki link for a list of people who are buried in the vault.
Either the 11th or 12th Phantom was the first Phantom to create the 'Vault of Missing Men' going on by the dates shown in the Vault and no other stories featuring earlier Phantoms.
Phantom Wiki URL