There could be an angel (or a demon) named Amenadiel, but, if there is, the Bible nowhere mentions him. The idea of an angel named Amenadiel comes from the grimoire Ars Theurgia Goetia, part of the Lesser Key of Solomon. Amenadiel is therefore a mythological figure.
Amenadiel’s mythical status does not prevent some people from taking him seriously, however. Various books of witchcraft and black magic give details about Amenadiel: he was the first angel created and is the brother of Lucifer. He sinned and was banished from heaven. Today, he is a high-ranking demon, the Emperor of the West, with vast numbers of lesser demons attending him. The Theurgia contains invocations of Amenadiel, along with conjuring techniques, spells, rituals, and other occult knowledge.
The name Amenadiel also shows up in popular culture. In the DC/Vertigo comic book series Lucifer, Amenadiel is a good angel who does battle with Lucifer. The Netflix series Lucifer also features Amenadiel as a central character. As in the comic book series, Amenadiel is on the side of good, although he sometimes joins forces with Lucifer to accomplish a mutual goal.
There is nothing profitable in the Key of Solomon, and the demonology and occult practices presented in it should be avoided by all followers of Christ.
We have Scripture as our guide, and the Bible does not give us much information about any of the angels, holy or demonic. If we needed to know more about the demons, the Bible would have told us. Complicated mythologies about spirit beings and their hierarchy are, in the end, nothing more than products of the human imagination, possibly influenced by demons. We don’t need to know the names of demons to resist them, to “be strong in the Lord and in his mighty power,” to “put on the full armor of God” and follow God’s command to “take your stand against the devil’s schemes” (Ephesians 6:10–11).