Hussar
Legend
IDHMBIFOM, does the flaming part of a flame tongue require a bonus action every round?
But, as to the question, yup, it's two attunement items in one - ring of fire resistance plus magic weapon. That, right there, would account for the increased rarity.
Also, it's probably a nod to AD&D, where a Frost Brand was a lot better weapon than a Flame Tongue (+3/+6 vs fire creatures vs +1/+2-4 depending on what you're fighting).
But, as to the question, yup, it's two attunement items in one - ring of fire resistance plus magic weapon. That, right there, would account for the increased rarity.
Also, it's probably a nod to AD&D, where a Frost Brand was a lot better weapon than a Flame Tongue (+3/+6 vs fire creatures vs +1/+2-4 depending on what you're fighting).