Mathew is a Wordwitch, and has the ability to persuade people and trace information. His powers are similar to Safi's Truthwitchery, much like Everane's Waterwitchery is similar to Aeduan's Bloodwitchery. However, he is not able to discern truth from lie directly. His powers make him an excellent informant, and he trades in information.
Mathew is from Cartorra, and is in the service of Dom Eron fon Hasstrel. He is Safiya fon Hasstrel's tutor, and later teaches Iseult det Midenzi as well. His Heart-Thread is Habim, a Firewitch, with whom he owns and operates a chain coffee shop. He uses the network of shops along with his Wordwitchery to trade in information.
He is described as being a calming influence on Safi. Unlike his stoic Heart-Thread, Habim, he is warm and much more open, leading him to be Safi's favorite tutor. Also, Safi's Truthwitchery seems to cancel out his Wordwitchery, so they can talk to each other without their respective witcheries influencing the conversation.
Mathew can use his witchery to make his words more persuasive. His powers also extend to written words, and is shown to make a magically binding contract with Prince Merik of Nubrevna in the first book. Additionally, he has the power to trace the origin of words, and so find the basis, if any, for the rumors he hears.