Portal Three Kingdoms was the third release of the Magic: The Gathering introductory level game sets known as Portal. As of October 2005, these cards are legal in the Legacy and Vintage formats. Portal Three Kingdoms also introduced an obscure game mechanic known as Horsemanship.
Because today these cards are legal in the Eternal formats, Legacy and Vintage, there are some very playable cards from this set that fetch a great deal of money, including Imperial Seal, Imperial Recruiter, Loyal Retainers and Ravagers of War. Some of these cards can cost a player as much as $200 USD, and many cards in these sets are worth at least several U.S. Dollars.