Anton Gris is a character from The Angel of Darkness.
Lara meets him in the Parisian Ghetto, in St. Aicard's Church. He is standing near the ring where Carl and Zak are practising boxing.
Officially he is working for a Fitness Studio, unofficially he the instructor for Bouchards men. Gris is originally from Marseilles, but he followed Bouchard to Paris. 
Lara can place a bet with him on his Gold Watch. If Lara chooses the winning boxer from Zak and Carl, she'll win the watch. If not, she loses 200 euros.