- Q: What happens to Call of the Unknown if there is no 'location other than your location' in play at the beginning of your turn? A: Nothing would happen. You would not shuffle it into your deck and take 2 horror; it would simply remain in your threat area. In other words, the condition of "f you did not successfully investigate the chosen location this turn" is not met because there was no chosen location.
Revelation - Put Call of the Unknown into play in your threat area.
Forced - At the beginning of your turn: Choose a location other than your location. When your turn ends, if you did not successfully investigate the chosen location this turn, take 2 horror and shuffle Call of the Unknown back into your deck.
Unless it's the back end of a scenario, you're going to end up tanking the 2 horror at some point. It's usually too much tempo loss to constantly move and investigate, even for Ursula. And once you take that 2 horror, you can look forward to drawing this again. Really that's what you're trying to prevent by satisfying that Forced trigger every turn- card draw denial. It is incredibly annoying to top deck this several times in once scenario. That said, take Mr. "Rook" to soften the blow. Yes, the card will recur even after Rook takes the two horror, but at least you pulled two other cards while drawing this one. It's a very thematic and engaging weakness to play around. Just take care you don't get hit too many times.