Question
Deceit in dice game
Answer
The dice game was considered as unfair and deceit because Yudhistira was not skilled to play.
Krishna says this in Karna parva when Karna asks for time to lift his car wheels and reminds as it is unfair to shoot on unarmed. Similarly, Krishna repeats again Shalya parva [1], while responding to Duryodana's claim that his warriors were slain unfairly.
Thou hadst, through Subala's son well-versed in dice, unfairly vanquished the virtuous Yudhishthira who was unskilled in gambling!
So, it's unfair and deceitful to gamble with someone unskilled.
[1] https://www.sacred-texts.com/hin/m09/m09061.htm
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