How do you get Fawkes in Lego harry potor?

In LEGO Harry Potter: Years 1-4, you can unlock Fawkes the phoenix by completing the story mission "The Chamber of Secrets." After defeating the Basilisk, Fawkes will appear and you can then access him. To use Fawkes, you need to complete a specific task where he helps you solve puzzles or reach new areas. Make sure to explore and complete all necessary story elements to unlock his abilities.