It was about a boy who is sort of bonded to a Phoenix. He can communicate telepathically with her. He goes on some sort of quest and meet some other kids who are bonded with these other magical creatures: a sabre tooth tiger, a winged wolf, a giant snake.
The kid bonded with the snake was not quite an ally at first and the main group was wary of him. There was some scenes in a mine I think. At the end they battle this dude at a volcano that wants all of the creatures for himself.
The Phoenix gets hurt and she falls in the lava and the characters think she’s dead, but she comes back stronger because it’s lava and she is strengthened by fire. I think there were four books in the series.