Torok is a Troll. He's the ex-husband of Eunice St. Clair. He also infiltrated the Potter family by replacing Harry Potter's little sister. He then attempted to create a fairy world within their apartment building. (Troll)
Torok was originally a Human spellcaster in an age of magic and fairies, before there were countries. In that time there was a balance between Humans and fairy creatures. Torok married Eunice St. Clair and taught her how to use magic. However, he later desired to break the balance between the Humans and the Fairies. This started a war, which the Humans won. As punishment, Torok was transformed into a troll.
Torok sought to restore the Fairy world. To do this, he infiltrated an apartment building in San Francisco, where he kidnapped young Wendy Anne Potter and replaced her.