Several months later, while investigating a haunted Dorm on Campus, Josh and Astrid were attacked by a Werewolf. Josh believes it to be the same one that attacked him. They were saved by Saul when he showed up during the attack and started shooting the beast with silver bullets. The creature was injured, and although Saul wasn't able to kill it, they were able to escape.
A few weeks later, Josh was taken to an alternate dimension and was to be sacrificed to resurrect a Demon Lord. However, right before the sacrifice, a full moon caused Josh to change and escape. The demoness casting the spell said that Josh would no longer be considered human, he was now a Lycanthrope.
Werewolves are humanoid/wolf creatures capable of transforming into a variety of related forms - such as a wolf, human, and a hybrid of the two. In hybrid form the werewolf stands around 7 feet and goes 300 or so pounds. They possess heightened strength, speed, senses and are able to heal most wounds almost instantly. Combined with their inch or more long claws and dagger-sharp teeth, they are extremely dangerous.
Silver seems to bother them, but it's not sure to what extent. Lore suggests that Fire and Aconite (wolfsbane) also may have an effect.