After reading through the Witch's Song I began to wonder why shouldn't there be a kind of "random encounter" deck? The adventure kind of gives a hint about something like that. It could be done quite easily - just using the already given environmental challenges presented in various adventures, throwing in the all-powerful key words (along the lines: urban, rural, wilderness, dungeon, rocky, watery ... etc.) and couple of "Random monster - draw a random monster from creature deck.
Then when needed they could be applied as Condition (or Environment) cards or drawn from a random deck.
How about it? Has someone already done it or should we do it as a community?