Unladen Swallow is a Curio that does not have a regular version for gameplay. Instead, the card and artwork by Heidi Taillefer only exist as this Curio version, complete with a unique and stunning fully Gold frame.
This card is a reference to the movie Monty Python and the Holy Grail (fitting for an Arthurian Legends set). In the film, King Arthur and his Knights approach a bridge guarded by a troll (Bridge Troll being another fun card that exists in the Arthurian Legends set). The troll throws out easy questions at first, but then hits King Arthur with the following tough riddle: "What is the airspeed velocity of an unladen swallow?" King Arthur replies, "What do you mean, an African or a European swallow?" This confuses the troll and launches it off a bridge. It's funnier in the movie. Watch it here: