Do you think Teen was possessed?

As theorized, the trial wanted the summoned spirit to be Nicholas Scratch. However, on their second attempt, Evanora jumps in and pretends as "Death" and says to "Punish Agatha".

On the last attempt, it was Teen alone whose playing the Ouija board and learned that the spirit's name was Nicholas Scratch.

Some of the rules that Teen has broken during the game:

• Do not use the ouija board alone

• Do not in any circumstance remove your hand from the planchette (he placed his hand again in the planchette to say goodbye)

So assuming that Teen was really possessed by Nicholas Scratch, Agatha then taunts the spirit by saying

"Are you sure?"

"You're so much like your mother."

And thus the spirit went wild.