What NIL Means in Duel
NIL is a bid to take zero tricks during the entire deal. Success scores +100 points; taking even one trick changes the result to -100. There is no partner to cover dangerous cards. The current Duel scoring applies this NIL result separately and does not add new bags for tricks taken on a failed NIL.
Why the Stock Makes NIL Risky
You start with 13 cards, but more cards enter your hand after each trick while the stock remains. A low starting hand therefore cannot guarantee a safe NIL. You may draw a high spade or a short-suit winner that becomes difficult to avoid taking. A complete deal lasts 26 tricks, and the zero-trick requirement applies to all of them.
Evaluate the Whole Risk
Look for low cards and enough lower alternatives within each suit. A high card in a short suit is dangerous because you must follow suit when possible. Reassess your exits after every draw and keep lower cards where they help you lose later tricks. Do not use NIL automatically because you are behind: compare its 200-point success-to-failure swing with a realistic numeric contract and the current score.