"Bohemian Knight" Doma is an infamous New World pirate who allied himself with Whitebeard.
Doma has a beard that seems to have lines that extend to his eyes. He also wears a large headband and a necklace with square jewels on it. He wields a sword. His neck appears to have a scar on the lower right.
A monkey is perched on Doma's shoulder.
Doma has managed to make himself an infamous reputation in the New World, and has managed to ally himself with Whitebeard.
He appears to be a swordsman, from the sword he wields.
Sometime in the past, Doma and his crew surrendered to Ace after he defeated them.
Doma and his crew are first seen, along with a fleet of 42 other infamous pirate crews, allied with the Whitebeard Pirates, attacking Marineford to save Portgas D. Ace from his execution.

Source: http://onepiece.wikia.com/wiki/Doma