For those put off by Jaded Officer's fairly mundane ability, or frustrated by Administrator's low strength, especially for a military card, Duelist provides a great stage two Roy Mustang that tailors to those who want to crush their opponents with overwhelming force early in the game. Duelist gains power to each attribute for every other state alchemist ally you have, which brings his already potent 4/4/6 line up in a hurry.
The best strategy with this card is, as described in the "combos" section, to get out as many state alchemist allies as possible to boost Roy. Military decks based around this card should generally focus on strength and alchemy, though a wits/alchemy approach could work with the right allies. Likewise, events should focus on flexibility, allowing you to beat your opponents at their own game. Personally, I would not recommend leveling up to his stage three if you are willing to play this card's ability straight, as all available level three Roys will probably be a step down in the power department.
State alchemists are your best friends in a Duelist deck. Furthermore, as Roy is neither hero nor villain at this point, you can run Kimblee and Ed together, and should do so. As alchemy will probably be your best attribute, cards like Shou Tucker: Proctor and Edward Elric: Researcher are a must. One tricky ally to run is Marauder: Masked Demon, who gains the keywords of all of your other allies, including the state alchemist keyword. As with other Roy decks, Hakuro: General and Rize Hawkeye: Sharpshooter are good non-alchemist supporter allies. For his level one, consider using Career Officer to boost the state alchemists you get out early.
Ways to counteract it:
Three cards can make life difficult for the Duelist. The first two, Stone Wall and Exhaustion, have the same effect of draining the wonderful bonus gained from your allies. The final one, In Over Your Head, is only a problem if you have increased Duelist's strength by more than four. Between attachments, state alchemists, and Hakuro, this is not difficult to do, so beware.
Simply put, this card can have some of the highest stats in the game, and can tangle with even level four leaders in almost any attribute when fully charged. With just an attachment or a single state alchemist ally, he can play most alchemy events, and a few allies more allow him to play almost every event in the game for free. While perhaps not a card for the "finesse" player, Roy's power is his calling card.
The primary weakness of this card is its fairly low command. While he can certainly fight and play events like a level three or four leader, a command of only seven really hurts the allies you can bring to bear. To make matters worse, some of the state alchemist cards you would want to pump Roy up are a cost of eight or more, namely Basque Grande: Brigadier General and State Alchemists: Dogs of the Military. While you could use a combo of Kain Furey: Master Sargent and Charismatic Leader to work around it, it might not be worth the events or other allies you have to sacrifice.
This card is available only in a standard foil, released only in the Blood and Water Roy deck, or as a clear transmuted card in Blood and Water.
Artwork and aesthetics:
Like many of the Roy cards from Blood and Water, this card depicts a scene from episode thirteen, during the Mustang/Elric duel. While I very much like the artwork, and think the screencap is great, I have to admit the flavor text could have been better suited to the warrior aspect of Roy that is being played up here.
Overall, this card is a solid 9 out of 10. The only thing holding it back from a perfect ten is the lack of command for playing deep into games, but overall the ideal leader for an in-your-face military deck.