Hooktail is the first major boss you encounter in Paper Mario: Thousand-Year Door
. You first see her as soon as you come out of the warp pipe that takes you to Petalburg, flying to her castle in the background. In Petalburg they tell you all about her and how she has terrorized the town. She's the reason for why Koops
joins your party, to finish what his father had started, slay the dragon.
Her castle is filled with the remains of koopas, some actually being dry bones and attacking you. She has a weakness, and that is anything that has to do with a cricket, since she once got food poisoning after eating one.
During the fight it may seem you had defeated her at first, but before you can land a final blow, she eats some of the audience and replentishes 10 hp.
After really defeating her, Koops' father comes out of her mouth. He had been living inside her since he got eaten when he set out to slay her and then, Mario and Koops receive the first Crystal Star.