How do you get past filch in slytherin dorm?

invisibility cloak.

Go to the pic of the fat lady on the wall there will be a scribble on the wall click on it and it will say Michael and then tell the lady that's the password she will open up next click on the black...

You need to buy a Slytherin character. (But you have to find one first.)Harry also obtains the ability to speak to some snakeheads.

By having a invisibility cloak like harry did.

you have to have unlocked a slytherin chatcter in the game and then change into them with the polyjuice potion adn then go to the common room entrance and press bhope this helped