The database has a set called "WLD" (Championship Prizes) with the cards of the Vintage Championship Event of Indianapolis where the winner is given an UNIQUE oversized card from the Power 9 list (Black lotus, Moxes...) The card from the 2011 Championship (Time Walk) is missing from the database.

More info here: http://www.magiclibrarities.net/468-rar ... index.html

Also, the card "Balduvian Horde" on that set is not related with the other cards (It was given on a complete different event and more than one copy of that card exist), so maybe you should put it on a different "special set" and/or change the name of "WLD Championship Prizes" to something like "GCV Gen Con Vintage Tournament" or something else more appropriate. A set called Championship Prizes is quite ambiguous because there are many special sets with cards awarded as championship prizes