We developed Rurik for 1-4 players, which we believe provides the optimal play experience.
Outside of needing many more components to accommodate a 5th player, there are additional gameplay considerations that need to be accounted for. We will be evaluating the response to Rurik and hope to offer an expansion that adds a 5th player (among other things) down the road, but it will not be part of the current Kickstarter campaign. Thank you!
Don't see the answer to your question? Ask the project creator directly.