The Wisp bonus round rule is one of the many rules that can be applied during the Bonus Round episodes.

If playing as the Robot, this rule can show up on any floor (more common on floors 2 and 3, though). Otherwise, it's a rare rule that only shows up on floor 2 for the other characters.

This rule is never offered if the Wisp is in the dungeon, likely because the Wisp wouldn't have any reason to use Fool's Fire.

Wisp

No duplicates! Matching dice vanish as soon as they are created.

When the rule activates, both fighters get the Vanish status each turn, which causes it to be such that whenever two or more dice match for either fighter, all but 1 of those dice will be immediately destroyed. This rule is similar to the rule in Compression Errors, but this applies to both fighters instead of to just the player.

This rule can be useful since the Cowboy will get less out of a Midnight Charm, but it can also hurt because dice duplication and any equipment with random dice manipulation will potentially remove otherwise useful dice. Additionally, it will greatly cripple a player's first turn if the Singer bonus round rule is active.