Managorger Phoenix is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Flying Managorger Phoenix can't block. Whenever you cast a spell, if Managorger Phoenix is in your graveyard, put a flame counter on Managorger Phoenix for each in that spell's mana cost. If Managorger Phoenix has five or more flame counters on it, return it to the battlefield and it perpetually gets +1/+1.