I've come across the incredible Arkham Horror Statistics spreadsheet that fans have contributed to. I have played a few expansions and I understand most of what is on there, but I'm confused with the "Dual-Color OW Battle" under the "Special Events" header of the Miscellaneous tab. What is this? I know that OW stands for Other World, but I'm not sure what it means otherwise.
I haven't found anything about it on the Arkham Horror wiki or a general Google search. The only thing I can think of that would be two colors is Gloria's ability letting you draw two cards in an Other World, which might or might not be different colors. But that doesn't really make any sense in the context of a battle.
So what exactly is a "Dual-Color OW Battle"?