The Tongue of Flames is one of the five fragments of the great Blackrock Obelisk of Pagan. It is Pyros's object of power.
When the Obelisk was shattered by the Guardian, the Tongue of Flames landed in the Cemetery, where the Necromancers found it and gave it to the Sorcerers many years later. They used it to bind Pyros to their will, effectively imprisoning him. It stayed with the master sorcerer in a line of succession, until the Avatar defeated Malchir in battle and took it in Ultima VIII. Putting it on the great pentagram, Pyros was freed and the connection to the Sorcerers broken.
He later used it then to drain Pyros of his powers, destroying him. It then melted into the other fragments, reforming the Obelisk.