Flame Tongue

Weapon (any sword), rare (requires attunement)

You can use a bonus action to speak this magic sword's command word, causing flames to erupt from the blade. These flames shed bright light in a 40-foot radius and dim light for an additional 40 feet. While the sword is ablaze, it deals an extra 2d6 fire damage to any target it hits. The flames last until you use a bonus action to speak the command word again or until you drop or sheathe the sword.

In these lists

Rare magic items
Magic weapons
Weapons table

Questions

Does the Flame Tongue require attunement?

Yes: it requires attunement.

How rare is the Flame Tongue?

It is a rare weapon (any sword).