Mictlantecuhtli

Mictlantecuhtli, also known as the Presser of Destruction is a bat-like demon that lives in the deepest caves of inferno and serves as a summon in Bayonetta 2. It is said to carry plague wherever it goes, it is also able to access an understanding of the world that no creature relying on its sight could see.

Book of Infernal Demons
"A gigantic bat that lurks in one of the darkest and deepest of Inferno's endless caves. It is said to leave trails of the plague wherever it goes. The protrusion on its head is not an eye, but a spiritual sensory organ that can allow Mictlantecuhtli to access the world in far deeper ways than beings who must only rely on sight alone."

Bayonetta 2
Michtlantecuhtli only appears in specific gameplay circumstances. It is most often seen when using Umbran Climax with Love Is Blue, Rakshasa, Chernobog or Shuraba equiped. It is also featured in Greed's Torture Attack where bayonetta summons Michtlantecuhtli to crush Greed from the top.

Trivia

 * Michtlantecuhtli is named after the Aztec god of the dead.
 * The Aztec Mictlantecuhtli is ruler over the lowest underworld, much like how Mictlantecuhtli is found in the deepest parts of Inferno, which may be another reference to the God it is based on.