This is Abaddon - angel of destruction, ferryman of Sheol, bringer of nasty mutant locust-thingamabobs and eventually the dude who's going to chain Satan down in Hell for 1000 years. Well, that's what St. John was told, who knows how accurate his sources actually were.
To most people he's Benny St. John (oh what a clever boy) and he's a cab driver in New York City. He actually works for the same cab company as Hati and they bond over heavy metal music. He's a quiet guy, likes watching people and tends to keep very detailed journals of every single thing he did and saw every day. For those of you who've seen Everything Is Illuminated, think of Jonathan's wall of "collections" only slightly less obsessive than that.
He would also like it to be clear that while the occult/esoterism and Satanism has adopted him in this new age, he still gets his orders from God. When they come in, that is. And while he feels a little too old for all this excitement, he's up for hitting a bar with just about anyone.