Eiichiro Oda's One Piece is filled to the brim with infamous and powerful pirates, many of them loosely based on real-life figures. Chief among them is Marshall D. Teach, better known as Blackbeard, currently one of the Four Emperors (or Yonko) and a former Warlord of the Sea. Quite a bit is known about Blackbeard; his backstory and powers have all been given a good amount of screen time. And being that he is probably Luffy's biggest nemesis (perhaps tied with Marine Admiral Sakazuki), it's fair to expect that Blackbeard and his crew will face down the Straw Hats imminently.
Compared to other Yonko, Blackbeard's crew is still somewhat mysterious. Their names and appearance are known, but many of them have yet to fight in major battles and thus their powers and oftentimes their backgrounds remain obscure. What can be said is that the nine pirates Blackbeard commands are extremely formidable foes in their own right, and shouldn't be taken lightly. After the time-skip, these nine crew members comprise Blackbeard's Ten Titanic Captains, each heading their own ship in Blackbeard's fleet.
The Original Crew
The Blackbeard Pirates' membership can be roughly divided into two camps. When Blackbeard is first introduced in the Jaya arc, he only has four followers. The remaining were among the most dangerous prisoners at the World Government prison Impel Down, who Blackbeard broke out prior to killing his former captain Whitebeard at the Battle of Marineford. Whitebeard's original crew consists of helmsman Jesus Burgess, sniper Van Augur, navigator and chief of staff Lafitte, and doctor Doc Q.
Burgess, who is often seen as Blackbeard's second-in-command, has been seen carrying out solo missions on behalf of Blackbeard, first hunting for the Mera Mera no Mi (Flame-Flame Fruit) in Dressrosa, and again infiltrating Baltigo, home to the Revolutionary Army. Burgess's powers are unexplained beyond the fact that he has immense physical strength, enough so that he easily won a battle royale in Corrida Colosseum. However, Burgess lost relatively easily to Sabo, the Revolutionary Army's second-in-command and Luffy's adopted brother. Prior to joining the Blackbeard Pirates, Burgess's background is completely unknown, a trait that he shares with most of its members. Burgess is the captain of the Blackbeard Pirates' FIrst Ship.
Very little is known about Van Augur, other than that he possesses excellent vision and speed, and is such a good sniper that he was able to shoot a seagull from an island so far away that the Straw Hats (who witnessed the bird get shot) couldn't see where they shot came from. Like Burgess, his background is completely unknown. Van Augur is captain of the Third Ship. Lafitte's background is partially known. He was a formerly a sheriff somewhere in the West Blue, but was cast aside for his excessive cruelty before joining Blackbeard.
Knowledge about his abilities is limited, but he is capable of sprouting wings to fly (possibly from a Devil Fruit) and can move at superhuman speed. Lafitte is captain of the Fifth Ship. Doc Q is a sickly man who rides an equally sickly horse, ironically named Stronger. He apparently has suffered from a terminal disease since childhood, but otherwise nothing is known about his past. In battle, Doc Q wields a giant scythe which he has used to devastating effect. Doc Q is captain of the Ninth Ship.
New Additions
After Blackbeard and his four original crew members visit Impel Down, they free five of the most notorious criminals locked up in the facility's lowest level, Level 6, all considered so dangerous that they have been essentially erased from history. The prisoners at Level 6 fought in a battle royale for the opportunity to leave with Whitebeard, and the five who join him were the survivors of that battle. Among these members is Shiryu of the Rain, Captain of the Second Ship and former Head Jailer of Impel Down. Shiryu was imprisoned for regularly murdering inmates, and is an extremely proficient swordsman. After the time-skip, he eats the Suke Suke no Mi (or Clear-Clear Fruit), which allows him to become invisible, making him even more dangerous. He gained this power after murdering its former holder, Absalom, a former member of the Warlord Gecko Moria's crew.
Catarina Devon is the only woman among Blackbeard's Ten Titanic Captains, and is in charge of the Sixth Ship. Little is known about her life before being imprisoned other than that she rivaled the Yonko Big Mom during the Golden Age of Pirates. Devon possesses the Inu Inu no Mi, Model: Kyubi no Kitsune, a Mythical Zoan Devil Fruit which allows her to transform into a nine-tailed fox. Sanjuan Wolf, who heads the Seventh Ship, is a gargantuan giant, dwarfing other members of his race due to eating a Devil Fruit which further increased his size. Due to his size, he possesses a massive level of strength, but his powers are otherwise unknown.
The most mysterious members of the Blackbeard Pirates are Avalo Pizarro and Vasco Shot, who head the Fourth and Eigth Ships respectively. Pizarro was once a tyrannical king in the North Blue before being imprisoned. Nothing is known yet about either of their powers, or about Vasco Shot's past before being imprisoned. Blackbeard also has a few lesser crew members about which very little is known, aside from their names and faces. The exact details of where and how in One Piece the Straw Hats will face down the Blackbeard Pirates is something only Eiichiro Oda knows for now. It should be noted, however, that there is exactly one member of the Ten Titanic Captains (including Blackbeard) for every Straw Hat, and it might be safe to assume that each will fight one another one on one.