The demon proceeds to cast a spell that prevents Twister from telling anyone about this. The spell did not prevent Twister from researching the occult on his own; this is how he finds a way to break the demon's original spell.
The demon cast a spell preventing Twister from disclosing this information. However, it did not hinder Twister's ability to study the occult on his own; thus, he found a way to counteract the demon's initial spell by conducting independent research.