Those would be Wild cost cards. I'm realizing now what the problem is.
The current paid version of Brute Fort includes the Auspice expansion. It also includes an updated rulebook clarifying rules and adding a new cost type, Wild.
I think the current non-paid version of the rulebook doesn't include the Wild cost explanation. (As without Auspice, there are no cards with Wild cost.) But this becomes a problem when the free homebrew expansion includes Wild Cost cards (Which, if you didn't buy the full game, just go unexplained)
Wild cost cards (The scribble ones) can be paid for with any resolve type from any hero, and may even be spent using the resolves from multiple heroes. (Say, 2 resolve from wanderer and 2 resolve from champion)
I might ask Alfred if I can add a Wild explanation to Harken, since it's an Auspice rule and Auspice is a paid product. Or if I should change the wilds in harken to other costs.