This is an expansion and requires the base game to play: Yes

Before the Black Throne is the sixth and final Mythos Pack in "The Circle Undone" cycle for Arkham Horror: The Card Game.

After your battle to close the rips in reality in In the Clutches of Chaos, you have left your city and your world behind, traveling an impossible distance, and yet you are still many leagues from the nighted throne where your ultimate foe stirs. As you are chased by your fate across the cosmos, you may be forced to bring "empty space" into play, losing the top card of your deck as you place it facedown to embody the seemingly infinite space that divides you from the rest of humanity.

This is not a location; it cannot be entered or investigated, and the only way to reclaim your lost card is to fill the empty space with a Cosmos location. These impossible places, drawn from the new Cosmos deck, do not have set places they must connect to. Rather, each Cosmos card has a connecting instruction you must obey in order to place it. Torn from all you know, it may be easy to surrender to the existential dread, but even if all you can do is delay the inevitable, the battle is not over yet!