MCU: What Is The Tesseract?

The MCU has introduced a number of important magical artifacts over the course of its plethora of movies, but there is perhaps none that has made as many appearances as the Tesseract. First introduced in an end credits scene in Thor (and then becoming more prominent in Captain America: The First Avenger and beyond), the Tesseract plays a big role in the MCU, particularly in the first phase. It comes back in the later part of the Infinity Saga as well, as it rises to even greater importance as an Infinity Stone.