What is the name of the creature who guards the entrance to the mines of Moria in the Lord of the Rings universe?

The creature who guards the entrance to the mines of Moria in the Lord of the Rings universe is called the Balrog. The Balrog is a fictional creature that was first introduced in J.R.R. Tolkien's novel The Lord of the Rings. It is described as a powerful and menacing demon that is feared by many.

In the story, the Balrog was originally a Maiar, a divine spirit, who was corrupted by Morgoth, the first Dark Lord. It was sent to Middle-earth to aid in Morgoth's war against the Valar, the divine powers who shaped the world. During the First Age, the Balrog was defeated and cast into the abyss, where it remained until the Third Age.

When the Fellowship of the Ring entered the Mines of Moria, they awakened the Balrog from its slumber. It pursued the Fellowship through the mines and eventually confronted Gandalf the Grey, one of the members of the Fellowship. In the ensuing battle, Gandalf was able to defeat the Balrog, but at the cost of his own life.

Despite only appearing briefly in the Lord of the Rings, the Balrog has become an iconic character in the fantasy genre. It has been featured in numerous adaptations of the Lord of the Rings, including Peter Jackson's film trilogy, where it was depicted as a massive, fiery demon.