Hogwarts is

You're on Scenario 1 of 7

As you walk the shack creeks
Letting out little silent shrieks
A glow in the window catches your eye
You look out and let out a small cry

Greenish smoke and putrid smell
A ghastly face in the darkest night
Looks like something straight from hell
The sign that gives you quite a fright

Ghoulish skull tinged with green
And eyes filled with emerald stars
From its mouth a serpent is seen
A creature filled with countless scars

What spell caused this to happen?

Riddles written by Allison Frederick & Kimmi Cranes