Thematic similarities aside, the choice seems pretty obvious. The thing you saw may have been a big wolf, it may have been a purple wolf, and it may have been a wolf made out of rubber, but there are two things that you're still pretty sure of: that WAS a wolf, and wolfs can't generally open doors. Maybe this thing can - you didn't get a good look at it, and for all you know it has opposable thumbs - but you still don't have anything else to go on, so you head for the opening with no door keeping it shut.
Stepping in cautiously, you see... well, nothing. The room is just as dark from inside of it as it looked from out in the hallway, and your instinctive search for a light switch beside the door turns up absolutely nothing. You aren't sure how good of an idea it is to just step into a room you can't see anything in when you're chasing after a potentially deadly monster, but you brush your concerns aside. At this point, it doesn't really matter whether or not you want to go back, because you can't actually see the way back out.
You feel your way along the walls and walk further and further into the room, but even after a couple of minutes of it you don't hit a single corner. Deciding that you might have better luck just wandering blind and aimlessly, you move away from the wall and take a couple of steps out from it. You fall over forward. It's not that the floor is slippery or made of something particularly loose - no, it's definitely solid, something you can say for sure after landing on it - but just a few feet from the wall it starts a sudden, steep incline. Excited that you're finally getting somewhere, you follow the incline downwards until you hit a corner where it meets another incline, the two of them traveling together and further down. Interesting: if the other two sides of the room are similar, then the entire floor is angled down towards the center of the room. Now the only question is what they're angled for.
Your curiosity unsated and insatiable, you decide to follow the floor right down until you reach the center, where you find...