Who is Luggage from The Light Fantastic and what is their importance?

Luggage is a magical suitcase that Twoflower bought in a magical shop in his own world. It has legs and a mind of its own. Luggage is exceptionally loyal and follows Twoflower everywhere, even going out of its way to find him when they separate. Often he saves the three characters from precarious situations. For example when Herrena captures Cohen, Bethan and Rincewind, Luggage entices Herrena's men with gold and then eats them up. At the end of the book, Luggage swallows the Octavo, so no more evil hands can get to it.