Murmur, also known as Murmus, Murmuur or Murmux, is the 54th demonic spirit of the Ars Goetia and a Duke of Hell, taking the form of a soldier with a ducal crown riding, depending on the source, a vulture or gryphon. A teacher of philosophy, and also a master necromancer, he is able to force the spirits of the dead to answer any question a conjurer might have.
The guardian of the first birdcage in Kagome Tower within Shinjuku National Park. He introduces himself as a once famed Great Duke of Thrones and states that he will pluck the Samurai's spirits from their bodies and make them dance eternally since they came to free the prisoner. He crumbles upon defeat.
Shin Megami Tensei IV Apocalypse
"One of the 72 demons of the Goetia, he is called the Great Duke of Thrones. He appears clad in blue armor, riding a gryphon, and wearing a crown. Philosophy and necromancy are his forte, and he can use any corpse as a vengeful spirit. He also leads over 30 armies as a Grand Duke of Hell."
—Shin Megami Tensei IV Apocalypse compendium
Murmur will first appear in Tsukiji Konganji on orders to retrieve Flynn from Lucifer so that Flynn can become the messiah for the demons. When the party refuses, he opts just to kill everyone and take Flynn by force.
Murmur is fought at Harajuku Shelter. After effortlessly defeating the party with powerful spells in a scripted event, Yuuka Tachibana gets devoured by demons and a poisonous gas is released. He is fought as a boss later in the game.
Devil Survivor 2
"One of the 72 demons of the Goetia, he is called the Great Duke of Thrones. He appears clad in blue armor, riding a gryphon, and wearing a crown symbolizing his station. Philosophy and necromancy are his forte, and he can use any corpse as a vengeful spirit. He also leads over 30 armies as a Great Duke of Hell."