The Burning Earth (The Burning Earth +1 in-game), also known by the name of Flame Tongue, is both a silver and cold iron long sword that has advantages against specific enemy types.
There's also a weapon called the Sword of Flame with a different strength requirement and no mention of additional augments to any creature races.
In TotSC the sword is trap-locked in a chest located in the master bedroom of Labyrinth Level 1 beneath Durlag's Tower; In BG:EE the sword's location has been replaced by the The Practical Defense and it's moved far away to Labyrinth Level 4, where the ghosts of Durlag and Islanne are lurking. The Staff of Striking is also found down in the vault.
|“|| Flame Tongue +1: The Burning Earth|
There was a time before Neverwinter was warm and before the great Anauroch was dry... or so it is said. Few relics remain to prove such an age existed, and fewer still have an identifiable purpose. "The Burning Earth" seems straightforward enough. It burns a victim with magical fire, and a cryptic rune seems to suggest that the power comes from the ground itself—but whomever constructed it remains a mystery. It looks a perfectly serviceable weapon, but something in the balance or grip is... wrong. It strains the forearm a touch, and does not fit the hand just right. It doesn't seem to hurt a warrior's performance, aside from the nagging doubt that the blade was not made for <PRO_HIMHER>... or any other humanoid.
- Like the Moonblade, this blade is also on fire when unsheathed, but this one has naturally colored flames