Cocoon:
You can see... some fairy citizens are being changed within these... cocoons,
but it's not too late... to stop them! Attack the cocoons, while they are still forming, and you will destroy them.
Otherwise, you can promote the mutation by injecting Glimmer into them channel where nutrients are supplied.

(To use Glimmer, target a cocoon and click Glimmer. To attack the cocoon, initiate an attack while pressing the Ctrl key. For a powerful attack, use your skills.)
Attack Launch a powerful attack