Can you temporarily close this location by summoning the henchman Vrykolakas if one of the stacks are already closed? When closing text states: "When closing a stack, summon and defeat the henchman Vrykolakas. This location remains open until both stacks are closed."
What does the "At this Location" power say? Doesn't it something about how to treat each stack? Perhaps as separate locations or something? I can't remember. But I think it might influence the answer to the question.
It says to treat each stack as a separate location.
edit: still waking up. Reread your question. If one of the stacks is already closed, I would think that you can temporarily close by having a character who is at the other stack fight a Vrykolakas.
That is what we ended up doing.
I think that sounds good. I've never liked that the location seemed to in one part tell you the stacks were like separate locations than in another talk about the card as on location.