Matthawa is the most powerful psyker in the Saurus Legion and the head of the Chapter Librarium. He is as old as any other Brother in the Legion, and knew Incarna when he was a Marine. The two go back a long way, and Matt still ribs the daemon about not being able to eat choc ice without it melting all over his hands.
He wears a massive suit of Terminator armour, with an Aegis suit, Psychic Hood and conversion field mounted into it. The armour is older than he is, and small pieces of the previous three Masters of the Librarium (except for Bob, who was only in office for three days before his disguise slipped and they shot him) are cast into it.
His weapons are also somewhat intimidating. In one servo-assisted hand he carries the Daemon Weapon Ke’ke’shequavara (kay-kay-shi’kwavara), a Force Sword with the unfortunate daemon prince bound inside. In the other he carries the first and only Assault Psycannon, a somewhat unimaginative weapon of his own devising. Only a supply of psi-damping material from Karos allows this weapon (which would, were they to learn of its existence, cause the brave men of the Ordo Malleus to throw their arms high in horror) to exist.