Go to the left and up a little, where you'll find an open door to the dungeons. Be careful of Professor McGonagall - she's hanging around. Enter the door, and GRAAAGH! The troll's around. Hermione and Ron run into a corner, so you must face the troll yourself.
First arm yourself with your Flipendo jinx to face the troll. Go left, where you'll see some small holes, and a huge pit at the very left. Don't fall down the huge pit, but if you fall through any of the small pits, you can still climb back up. To fight the troll, make sure he's as close as possible to the large pit, then dodge his club and wait until he brings his hands up to roar wildly. Then cast Flipendo at his belly, and he will be repelled back a short distance. Repeat until he falls down the pit. Then Snape, Quirrell and McGonagall rush in, and nearly reprimand you, but after a hasty explanation from Ron, reward you with 50 House points instead.
"You defeated the troll! It smells really bad! But Hermione is safe now, and so is the rest of Hogwarts."
You appear back here, and Hermione thanks you and tells you to go up to Transfiguration Class on Floor 1. Follow her to Floor 1, and go to the classroom which is on the right side of Floor 1.
Inside, Professor MacGonagall teaches you Avifors, which tranforms certain things into birds. Follow her wand movements and extra two sets of wand movements for more House points. After doing that, you will start the Avifors challenge. Go into the Room...
You can turn certain objects (usually lying on pressure plates) into birds with a quick cast of Avifors on it. It will release the pressure plate, opening doors or flipping bridges.
1. Go forward and cast Avifors on a stone-like thingy on the pressure plate. It will turn into a bird and fly off, opening a door. Enter the new room, lure the Doxies into the Tentacular, and grab the easy Golden Star behind the Tentacular. Now go up and out of the room.
2. Go right, past some blue carpets and restoring health with jellybeans you find along the way. If you go a little downwards of the blue carpets, you'll find a Flipendo block across the chasm. Push it and go along the narrow corridor to the right leading downwards, and knock out the blue gnome wandering around with two Flipendo jinxes. Grab the second Star in the corner.
3. Now go to the left, pushing a barrel out of the way to see another stone like object on another pressure plate. Use Avifors yet again, and another door will open. Go to where you found the blue gnome and go downwards to find the open door. Now go through the door and to the left to get an easy Golden Star.
4. Go right and up through another doorway, and take the left path upwards. Knock out the two blue gnomes and take the fourth Star.
5. Now go to the right and downwards to a dead end. You should see yet another stone-like object on a pressure plate. Avifors yet again, and go backwards out of the dead end, and find the open door which leads to a stone gargoyle and a pressure plate. Cast Flipendo on the gargoyle, and when it moves onto the pressure plate, go through the open door quickly. Now get the fifth Golden Star.
6. Go to the left and up through another open doorway, and if you need health, open the chest for a bag of Jellybeans. From where you are in the area, you should be able to see two Flipendo blocks across the chasm. Push them with Flipendo, cast Avifors on another stone-like object to open another door, then go downwards through the newly opened door. From there, cross the path cleared from the pushing of three Flipendo blocks previously, and get the last Golden Star. Now double back to the open door which you first went through to start your Avifors Challenge. Done!
"You overcame the Avifors Challenge! Your heart soars like a hawk, or perhaps more like a finch."
When you exit the classroom, Hedwig, your snowy owl, swoops in and brings you a scroll. Read it, and you'll find Hagrid wants you over at his house to collect Flobberworm Mucus - double time. So go down and out of Hogwarts, across the grounds, through the garden to Hagrid's house. I don't have to tell you how to do it gain, do I?