Who is Oyster from Lullaby: A Novel and what is their importance?

Oyster is Mona's boyfriend. We never learn his real name. Oyster is a strong supporter of animal rights, and he believes that the world should be destroyed..... something that would allow one man and one woman to start over and create a more perfect world. Oyster believes the grimoire will serve this purpose, but he soon finds that the spells he needs are not in it. He and Mona then use the grimoire to wreak havoc on the country.