The Banshee bonus round rule is one of the many rules that can be applied during the Bonus Round episodes. It can be offered on floors 4 and 5 for any character, as long as either of these conditions are met:
The rule cannot appear at the same time as the Warlock Bonus Round rule.
When the rule activates, the status effect Cursed changes to Cursed?, which causes equipment to have a 50% chance to swap target once inflicted.