Brook was once the captain of a fencing squad in a far away kingdom, which is where he learned his signature fighting style. He eventually ended up leaving to join the Rumbar Pirates, a pirate crew led by a man named Yorki. One day, the Rumbar Pirates came upon a baby whale left all alone, and they played a song to cheer it up. This caused the whale to follow the pirates around, and they decided to name the whale Laboon. However, when the Rumbar Pirates entered the Grand Line, an extremely dangerous part of the sea, they had to leave Laboon at the entrance to keep him from getting hurt. They promised that they'd come back for Laboon once they were finished, and sailed into the Grand Line. This led to half of the crew getting killed by a disease, including Yorki. After travelling into the Florian Triangle, Brook and the Rumbar Pirates were attacked by pirates with poisoned weapons, leading to each of them dying off one by one. However, Brook had previously eaten the Yomi Yomi no Mi, a Devil Fruit that brought the eater back to life after death, so he would come back after he died. After his death, Brook's soul managed to find its way back to his body, which took so long that his skin and flesh had rotted off his body, leaving Brook an undead skeleton. For many years, Brook was forced to sail alone, with nothing but the corpses of his friends for company. Eventually, Brook encountered a pirate crew known as the Straw Hat Pirates, led by Captain Monkey D. Luffy. After helping them defeat Gekko Moriah, one of the seven warlords of the sea, Brook accepted their off to join the Straw Hats, becoming the crew's musician.
Yomi Yomi no Mi: The Yomi Yomi no Mi is one of the Devil Fruits, magical fruits located all over the world that, when eaten, grant the eater superpowers. Brook's Devil Fruit, the Yomi Yomi no Mi, has the power to revive the eater after death once, which allowed Brook to come back to life after his death. The fruit's energy is what keeps his soul bound to his skeletal body, keeping it intact. If one of Brook's limbs or head is removed, the fruit's power will instantly reattach it. Brook can also separate his soul from his body to interact with others, with the cost of leaving his body helpless, feel the souls of others, eat and poop like a normal person, and conjure the chills of the underworld, which he can channel through his sword to freeze enemies, or use to shoot freezing ice blasts.
Skeleton Physiology: Due to his skeleton body, Brook's physiology is very different than a human's. By drinking milk, he can heal broken or fractured bones. He isn't bothered by extreme heat or cold, and he's resistant to electricity. He can also fall from great heights without harm, and store objects in his hollow skull.
Hanauta Sancho: Yahazu Giri: Brook's signature move, a slash that moves so fast that the target doesn't even realize they've been cut until Brook sheathes his sword. Depending on what Brook wants to do, the slash will either instantly kill the target, or incapacitate them.
Quinte Tierce Fantasia: After using Party Music to make the enemy drop their guard, Brook uses Hanauta Sancho: Yahazu Giri to cut down the distracted opponent.
Kasuriuta: Fubuki Giri: Brook imbues his sword with the chills of the underworld before using Hanauta Sancho: Yahazu Giri, freezing the opponent's blood and cutting them apart.
Ekakiuta: Hitoyogiri: A version of Hanauta Sancho: Yahazu Giri that involves imbuing Brook's sword with the chills of the underworld for three freezing cuts along the foe's torso.
Aubade Coup Droit: A thrusting technique that fires a bullet of air from the sword, which is strong enough to bust through walls.
Prelude: Au Fer: Brook slashes the enemy's weapon to disarm them.
Gavotte Bond en Avant: Brook propels himself forward for a dashing strike strong enough to draw blood from a dragon.
Polka Remise: Brook does a rapid barrage of stabs at extremely high speeds.
Swallow Bond en Avant: An aerial version of Gavotte Bond en Avant that moves downward instead of forward.
Nemuriuta Flanc: Brook swipes his sword over his violin's strings, playing a soothing song that causes enemies to fall asleep.
Party Music: Brook uses his music to hypnotize the enemy into thinking they're at a party, causing them to drop their guard and making them vulnerable to suggestions.
Soul Parade: A defensive backhanded slash used to block attacks.
Eisbahn: A swift drawing and sheathing slash that freezes the ground beneath the opponent, making them lose traction.