Fossa

Fossa is the commander of the 15th division of the Whitebeard Pirates.

Appearance
Fossa is a large and muscular older looking man, with a bald patch on the top of his head, a mustache, a scar running diagonally across his face, and seen smoking a cigar. He has Whitebeard's symbol tattooed on his right biceps, along with three little circles, and he wears a sleeveless jacket.

Abilities and Powers
As the commander of the 15th division, Fossa has authority over the lower-ranking subordinates. Fossa seems to be a swordsman, although his exact level of ability remains unknown, however it is presumed quite high. He wields a katana with a square shaped hilt, and was somehow able to engulf the blade in flames. Whether this ability stems from a Devil Fruit or other method is currently unknown. Also, like the rest of the Division Commanders, he is probably very strong, since Jinbei mentioned that each Division Commander possesses the "strength of 100 men".

Marineford Arc
Fossa first appeared when Whitebeard arrived at Marineford in order to save Ace. He landed on the ice created by Aokiji along with the other Commanders, and started the attack, slashing enemies with his flame-covered sword. He was seen again when Admiral Kizaru kicked Luffy: he assaulted the high-ranking Marine with other Commanders, giving Luffy a chance to carry on. Later, he was shocked at witnessing Squardo stabbing Whitebeard in the chest, and when his captain's quake-attack failed to destroy the siege wall, he commented on the unusual iron composing it. He entered the plaza behind the wall with the others, and was seen fighting alongside his comrades. He later joined Jinbei and other Commanders in protecting Whitebear'd back, and he was the one to reveal that both his captain and Red-hair possessed Haōshoku Haki. He appeared shocked when Whitebeard declared his will to sacrifice himself in order to save his "sons", and witnessed shocked Admiral Akainu piercing Ace with his magma-fist. When the latter died, he appeared angry, declaring that it couldn't be really happening. When the Blackbeard Pirates killed Whitebeard, he was seen crying incredulous, his cigar falling from his mouth for the first time. When Akainu resurfaced from the ground, he commented on his ability to melt the rock, and was among the others, when they faced off the Admiral in order to save Luffy. He was last seen mourning the results of the war along with the other Whitebeard Pirates.

Trivia

 * "Fossa" is the Italian word for "Pit", but it could also mean "Grave". It's also the name of an animal species native to Madagascar, the Fossa.
 * Fossa's flame sword is similar to Makugai's electrical sword.