Some early Christians believed some pretty weird things.
The First Epistle of Clement gives us an example. It was written around the same time as Revelation and was widely received in the early church, even being included in some early Bibles (Codex Alexandrius) and listed as a book of the Bible in an early canon list (Canon 85, in the Apostolic Canons).
In this epistle the author articulates that he believes the magical Phoenix to be a real bird.
“Let us consider that wonderful sign which takes place in Eastern lands, that is, in Arabia and the countries round about. There is a certain bird which is called a phoenix. This is the only one of its kind, and lives five hundred years. And when the time of its dissolution draws near that it must die, it builds itself a nest of frankincense, and myrrh, and other spices, into which, when the time is fulfilled, it enters and dies. But as the flesh decays a certain kind of worm is produced, which, being nourished by the juices of the dead bird, brings forth feathers. Then, when it has acquired strength, it takes up that nest in which are the bones of its parent” (1)