Dirth digs a bad mood. He thrives off them. He breathes them in.
He spends the majority of his time visiting places where he's most likely to find them. Places like the parking authority office, music venues with cancelled headliners, courtrooms, and traffic jams.
The more irritated people get, the more energetic Dirth feels.
He never directly contributes to the storm clouds over the heads of those he watches. It's more satisfying to stumble upon the brooding beings and lap up their negative energy without expending effort.
Lucky for him, there's an endless supply of grumpiness in this world. He'll never go hungry.