Duel on Banaro Island

Banaro Incident: An event that took place between chapter 440-441

History
This event's origin can go way back to the time when Blackbeard was under Whitebeard in attempt to search for a Fruit he desires. One day a 4th division captain name Satchi found the fruit, for Blackbeard to claim it, he killed Satchi. Blackbeard took the fruit and fleed. Ace was assigned to go after him and kill him.

Banaro Invasion
Blackbeard and his crews invades a small isle called Banaro Island. They knock out and kill most of the citizens residing there, after which they proceed to plunder the island. Most citizens run to the hills, away from the town to escape from the Pirates. Blackbeard had heard that Luffy has a Bounty of 300,000,000. Blackbead and his crew prepares to leave only to be stopped by Ace who was sitting on the building, telling him to wait up.

Heat is Up
Blackbeard attempted to get Ace to join his crew but he refused. After that, Van Auger rudely shot at Ace, next Jesus Burgess lifted an hotel building and attempted to smash Ace only for him to use his Mera Mera no Mi ability to burn the buliding before it hit him. Blackbeard angrily told his crew to stand down as a fireball suddenly struck him. When Blackbeard stood up, he ordered his crews to leave the town while he takes care of Ace. Blackbeard knew why Ace wanted to kill him and made no excuse of it. Blackbeard explained why he killed Satchi and unleashed a dark energy; exclaiming "I Am Darkness!!"

The Duel
Blackbeard proceeded to use his Yami Yami no Mi powers to swallow the town, intentionally missing Ace, then expelling it later with the dark aura around him swirling and violently releasing the remains of the town as a demonstration of his power. However, Ace is apparently unimpressed, and uses his Hotarubi: Hirudama (Firefly Fire: Body in Flames) technique with his Mera Mera no Mi powers, and was mildly surprised that the attack couldn't just pass through him as he is a Logia Devil Fruit user. Blackbeard consumed the flames with his dark aura, stood up and explained that his absorb everything, including knives, punches, flames etc. In fact, he perhaps takes even more damage than a normal human. But in exchange for that, he used his Kurozu technique to grab Ace's body and activate the Yami Yami no Mi's most devastating feature: The power to nullify any Devil Fruit powers upon touch. After Ace realized he couldn't use his Logia fruit powers, Blackbeard delivered a powerful punch to the stomach, smashing onto the remains of the town. Blood came spilling out of Ace's mouth, realizing he felt pain for the first time in a long while.

Blackbeard gloats that after exposing the "weakness" of all the so-called overconfident Devil Fruit users, he cannot be defeated, because his ability is truly the power of the "Devil". However, Ace pointed out it only works if Blackbeard touches him, to which Blackbeard counters he has already proved he cannot escape him, and used his Kurozu technique to attempt to grab him again, but Ace proved otherwise, and countered by throwing his Shinka: Shiranui (Sacred Fire: Mysterious Light at Sea) technique in the form of two fire lances into Blackbeard's chest, forcing him to punch Ace on his neck. Ace was again thrown into the town's remains and Blackbeard attempted to consume the flames with his powers. Ace noted if he takes a hit like that, Blackbeard will break his neck, and immediately retaliated from a distance with his Juujika (Cross-Fire) technique, as Blackbeard after successfully consuming the fires, took it head on.

As the battle rages, Banaro Rocks collapses at the amount of power both combatants are using. Both Ace and Blackbeard are exhausted, but it seems that Ace had is truly worn out. Blackbeard gives him one last chance to join Blackbeard's crew, but stubborn and determined to the end, Ace refuses. Blackbeard impressed by his strength, expresses his mild disappointment and says the world could have been yours for the taking, before unleashing a massive dark shroud. Ace at the same time unleases his own ultimate technique: Dai Enkai: Entei (Flame Commandment: Flame Emperor). Both prepared to fight to the death, "The Sun" and "The Night" literally clash, forming a massive explosion of energy that almost consumed all of Banaro Island.

Aftermath
Apparently, the Banaro Incident was the trigger of a great event yet to come on the Grand Line. Later on, it is revealed in Chapter 450, that Blackbeard emerged as the victor and Ace has been taken to Impel Down. In Chapter 473, Bartholomew Kuma confirming to Gecko Moria that Blackbeard is the newest member of the Shichibukai. In Chapter 490, The card Luffy was given to by Ace was revealed to be a Biblicard by Lola the Proposer, and it starts burning, meaning the owner's life is in danger. In the Sabaody Archipelago, the public execution of Portgas D. Ace was announced to commence in the location within ten days. As predicted, Whitebeard, who is Ace's captain will not take this news lying down and the World Government seems to be fully aware of that. The "great event" on the Grand Line is thus implied to be the imminent war between the World Government and the Whitebeard Pirates, with the Shichibukai and many of the Marines as the World Government's infantry.