Dr. Filangieri is a medical practitioner with an office in Edinburgh and the ability to do some form of magic, as he summoned several people out of Bastien's soul with an elaborate magic circle. He is Italian and fairly frequently slips Italian phrases or terms into his speech.
Filangieri is a very friendly, easy-going individual, though he worries David somewhat -- but even David considers him an ally, and one whose experiments on him have helped him improve. Filangieri is also narcoleptic, absent-minded, unkempt, and generally distracted. He also talks to himself a lot.
At the end of game 6 Filangieri confronts Asmodeus before Asmodeus can return to Lucia. He reappears in game 7 having travelled to the US apparently to help David, who he has been out of contact with since David woke up in his body and has been 'protected' by demons. But shortly after separating from the players, they return to his hostel and find signs he is on the run from -- or chasing -- something, and he has not been seen since this obvious speedy departure.