Built underneath Kotal's Koliseum, with a descending/rising wooden elevator in the center and a set of descending stairs built behind it, the Beast Pen contains many large caged pens, which inside contain some of the deadliest beasts lurking in all of Outworld. A large beastmaster leads the next animal or pack of beasts to the large platform elevator directly in the center of the pen, and once the animal is inside, a second slave will begin turning a large mechanical wheel to begin raising the platform into the arena above, where the beast will be unleashed upon the current competitors.
The Koliseum Beast Pen contains four stage interactions. From farthest left to right they are as follows:
- The furthest left and right walls can be run up and jumped off of to escape corners.
- A bucket of meat that can be thrown at the opponent.
- A large rib from a piece of a dead beast that can be used to smash the opponent's head, then stabbed into their abdomen, before following up with a strike across their face.
- In Johnny Cage's announcer voice one of his nicknames references "Fantastic Beasts" as in the 2017 film.