Each one of the six Colt Express: Bandits expansions allows the players to compete against the game itself, which is operating under the rules of that particular expansion. A new story is told each time as every expansion creates a specific goal and new actions for the bandit played by the game. That bandit may win, and if that happens, all the players lose. Thus you need to work together against this "bot", while keeping in mind that in the end, there is only one winner — the richest bandit, of course.

In the Tuco expansion, Tuco does not want to meet the Marshal, his former friend, against whom he bears a grudge.

Tuco's Fire and Punch hit all the possible targets, included Belle. The Swap action swaps Tuco and the Marshal's places, while Tuco's Marshal action takes the Marshal away from Tuco. If a player plays an action that brings the Marshal to the same location as Tuco, he receives a Wanted token (worth $500). At the end of the game, Tuco's loot is worth $250 per bullet he has shot.