Flametal and its ore is available in vanilla, but the Dyrnwyn is not (or, at least, not by normal means - it can only be created by activating devcommands and using the spawn command from the console). It's like the "Killsaber" from Knights of the Old Republic II - a "cheat" weapon in alpha that still exists in the game files, but is technically disabled and therefore not available through any normal means, not even the recipe.