A mythical ally
Fawkes is a phoenix and the pet of Dumbledore, the principal of the Hogwarts School of Witchcraft and Wizardry in the Harry Potter universe. We first meet him in the second book and movie of the saga when Harry Potter visits Dumbledore in his office. He arrives at the moment when Fawkes goes in fire before being reborn as a baby and starting to grow up again. Dumbledore teaches him the incredible properties of the phoenix that will be very useful to him later on. The fact that its tears have healing properties and that it can carry hundreds of pounds on its own. And indeed, when Harry will have to fight the basilisk later in the movie, the Gryffindor sword will present itself to him accompanied by Fawkes who will blind the beast and heal Harry before helping him, Ron and Ginny to escape from the tunnel. We will see Fawkes a few times until we see him fly away and regain his freedom after the death of Dumbledore at the end of the sixth film.