How do you get magoagoll in LEGO Harry Potter?

You can't get a "magoagoll" in LEGO Harry Potter. There is no item or character with that name in the game.

It's possible you're thinking of a different item or spell, or maybe you're misremembering the name.

Could you please provide more context or clarify what you're looking for?

For example:

* What game are you playing? (LEGO Harry Potter Years 1-4, Years 5-7, or another game?)

* What is the item supposed to do?

* Do you remember any other details about it?

With more information, I can help you find what you're looking for.