Blackbeard is one of the Four Emperors of the Sea. Before becoming an Emperor, Blackbeard used to be a member of Whitebeard's crew, and he avoided being promoted to stay off the radar of other pirates. Currently, he is among the strongest characters in One Piece.
Considering that many fans strongly believe that he is the final villain of the series, it is plausible to assume that he might get even stronger before his clash with Luffy. Blackbeard is an enigmatic character and much of his past remains a mystery, so what is it that he hopes to accomplish?
Scheming To Be The Pirate King
Blackbeard rarely reveals his goals and most of the time he keeps them secret until it's time to strike. Due to this reason, there is a great deal of confusion among some fans about what his final goal is. Is it to become the wealthiest or the strongest in the world, or is it something else?
On just one occasion, Blackbeard has made it clear that his goal is to become the Pirate King.
This happened during his confrontation with Ace on Banaro Island. Before their fight, Blackbeard tried to persuade Ace to join his crew, and one of the reasons that he provided was that the era of Whitebeard was over. So, it would be better to ally with someone stronger. It was at this time that Blackbeard revealed that he wanted to become the Pirate King.
Hunt For Power
Blackbeard has already taken numerous steps in his quest to become the Pirate King. He started his journey when he was still a part of Whitebeard's crew. Blackbeard was biding his time in order to obtain the Yami Yami no Mi, and once Thatch found it, Blackbeard wasted no time in killing his crewmate and fleeing.
It didn't take long for Blackbeard to start his own crew. The second step in the plan was to rise to the status of a Shichibukai. Initially, he had planned to hand over Luffy to the World Government in exchange for a position, but he changed his plans because Ace wouldn't let Blackbeard harm his younger brother. So, Blackbeard traded Ace to the Marines, and it granted him a position in the Shichibukai. When the entire world was focused on the events taking place in Marineford, Blackbeard and his crew made their way to Impel Down.
Blackbeard wanted to increase his crew's power, and what better place to find the most infamous criminals than in the most secure facility in the world? Blackbeard went to Level 6, where he asked the criminals to fight each other for an opportunity to join his crew.
This led to a massacre and eventually, Blackbeard acquired several new members. With his job done, Blackbeard headed to Marineford to find the next piece, which was Whitebeard's Gura Gura no Mi. Given Whitebeard's condition, this was the most opportune moment for Blackbeard to steal the mightiest paramecia type devil fruit. Despite a minor hiccup, Blackbeard managed to gain his former captain's devil fruit.
Becoming A Yonko
After the Paramount War came to an end, the world was in a state of shock because of the events that took place in Marineford. However, Blackbeard was already plotting to achieve his next goal, which was to become one of the Four Emperors. So, he engaged in war with the remnants of the Whitebeard Pirates, which came to be known as the Payback War. The victors of the war were the Blackbeard Pirates, and this effectively cemented Blackbeard's position in the Four Emperors.
With the position of an Emperor, Blackbeard had more freedom, and he could do as he pleased. Blackbeard's main goal became to gather as many devil fruits as he could. The first instance where the readers saw the Blackbeard Pirates actively pursuing certain devil fruits was in the Dressrosa arc. It was revealed that Jesus Burgess had come to Dressrosa to get his hands on the Mera Mera no Mi, which belonged to Portgas D. Ace. Unfortunately for Burgess, Sabo was also competing in the tournament, and he ended up winning it.
After losing out on the devil fruit to Sabo, Burgess' plan changed to killing the Revolutionary Army's chief of staff. It is unknown how Burgess was going to steal the devil fruit, but it is safe to say that it is a trick that only the Blackbeard Pirates know about. So far, the Blackbeard Pirates have already managed to get their hands on the Suke Suke no Mi and the Inu Inu no Mo, Model: Kyubi no Kitsune. The Suke Suke no Mi belonged to Absalom, but the Blackbeard Pirates murdered him and gave the devil fruit to Shiryu. The Inu Inu no Mi, Model: Kyubi no Kitsune is a mythical zoan type devil fruit, and it was eaten by Catarina Devon.
A few chapters ago, the Blackbeard Pirates were seen on Amazon Lily, and this time they were being led by Blackbeard himself. This was an indicator that the devil fruit was important to them, and also that Blackbeard didn't trust his crewmates to beat Boa Hancock. However, Blackbeard was forced to retreat because of Silvers Rayleigh. Instead of returning empty-handed, Blackbeard took Koby with him. The hunt for powerful devil fruits is definitely intriguing, and it is probably because Blackbeard believes that they will help him realize his dream of becoming the Pirate King.