Who is Usurer from The Mysterious Portrait from The Diary of a Madman, the Government Inspector, and Selected Stories and what is their importance?

A usurer is a money lender who tends to charge high rates of interest. The usurer in the story remains unnamed, and unlike many in his occupation, gives loans to people at reasonable rates. The loans, however, come with a price that most borrowers do not anticipate as it causes them people to become dark, angry, and envious. Many of these people even die horrible deaths.

Before his death, the usurer commissions a portrait of himself, believing it will make him in a sense..... immortal. Before the portrait is complete, however, the artist senses the evil and stops. Unfortunately, he keeps the painting in his possession, and over time, he becomes filled with dark envy and anger. Later, he loses his wife and children and comes to believe the portrait is to blame. In the end, the artist enters a monastery and asks his son to find the portrait and destroy it.