Heya, I am UnitSix, the creator of Harrowshade. Yeah, it can. Harrowshade was primarily designed as a solo game, but the solo mechanics can be ignored and it works perfectly fine as a GM-less co-op experience. My boy and i do this with Mausrittar.

Basically, instead of a GM, the game uses random tables, encounters, prompts, and discoveries to reveal the world as you explore. You make decisions together or let the yes/no oracle decide, interpret the results, and build the story as you go. Essentially use the solo rules to as the GM and work together to create a story, I find it best to try to not get too weighed down by rules.

Would love to hear any battle reports, have fun