Flamewake Phoenix Bug

Abracadavers

If you don't have enough mana in your hand to pay to return Flamewake Phoenix at the end of your turn, you are still presented with the option to return it. Selecting to return it will put it onto the battlefield without you needing to spend mana. This includes if you don't have any cards in your hand at the end of your turn. I have confirmed the behavior myself and also witnessed the opponent AI using it in this way.