Matthew Maule is much harder to pin down than his nemesis, Colonel Pyncheon. We really don't know much about him except that he is a carpenter and he's stubborn as a mule. He has a small patch of land that he cleared by hand, and he sees no reason why a rich bully like Colonel Pyncheon should be able to drive him off of it. (Quite right!) It takes a rash of witchcraft trials for Colonel Pyncheon to find a way to get Maule's property out from under him.
Even after his successful land grab, it's up in the air whether Colonel Pyncheon has actually won this fight with Maule. Yes, Colonel Pyncheon has found a way to build his grand mansion on the land he wants, but the spring of clear water that made the land so valuable has been polluted by the building process. Not to mention that Colonel Pyncheon has left his whole family with a mark of shame as a result of his (for all intents and purposes) murder of Matthew Maule.
Matthew Maule's character isn't only ambiguous because we don't know very much about him. He is also hard to pin down because he was executed for the crime of witchcraft. The fact that he is a convicted wizard gives his name an aura of fear and awe for Salem residents that Maule probably didn't inspire during his life.
There are two elements of legend that attach to his name: first, he is supposed to be able to control people's dreams. The House of the Seven Gables is full of hypnotism, which was cutting-edge science as the time. While it might appear as magic to more superstitious folk, it was also considered rational study in the 19th century. After all, Mr. Holgrave gives public lectures on hypnotism, and he decides that he is "probably as much a wizard as ever [Matthew Maule] was" (21.22).
Second, there is the famous curse – "God will give him blood to drink!" (1.4). The idea of the curse seems reasonable because, after all, the Pyncheons do appear to be operating under a gloomy cloud. The whole family has been on the decline for generations. And then there is the odd manner of death that strikes Colonel Pyncheon, Uncle Jaffrey Pyncheon, and Judge Jaffrey Pyncheon – always sudden, and always with a bit of blood around the throat. So was Maule in fact a wizard?
Mr. Holgrave speculates (undramatically) that the Pyncheon family has a genetic tendency towards strokes. He also thinks that Matthew Maule was aware of the Pyncheon family's hereditary illness, with this unusual symptom of the bloody neck. So Matthew Maule wasn't a wizard; he was just a wily, vengeful guy who chose precisely the right words to make it seem he was cursing them. That, at least, is Mr. Holgrave's conclusion.
We're a little less sure than Mr. Holgrave: maybe Matthew Maule did have some witchy abilities. It's completely characteristic of Hawthorne that he weaves together realism, fantasy, psychology, and the supernatural into Matthew Maule's story. One glimpse at his short story collection Twice-Told Tales – especially the story "Dr. Heidegger's Experiment" – will show his repeated interest in using the supernatural to discuss themes of age, human nature, and the various miseries of human life. After all, The House of the Seven Gables is a "romance" and not a realistic novel (source). Whether or not Matthew Maule is or isn't a witch is less important that the effect his ambiguous character has on the book's tone and plot.