The Inventor bonus round rule is one of the many rules that can be applied during the Bonus Round episodes, offered only if playing as the Inventor. It has a chance to spawn on floors 2 and 3 for the Inventor, but is more likely on floor 2.

The Inventor

Reduce scrap choices to two. The second choice is hidden.

When the rule activates, after winning a fight, the Inventor is only able to choose from two items to scrap from instead of three. The first item will be shown to the player, but the second item will be hidden and chosen at random from the other items. This is the same scrap rule that is used in the Parallel Universe (Inventor) episode.