Boss

"Boss" is a master thief from the South Blue and the person that raised William. According to Trevor, he murdered William's biological parents. He has used multiple aliases throughout his life and his real name is unknown.

Appearance
His original appearance before being captured by Trevor, is currently unknown other than having black hair and a beard. After being experimented on by Arzen, Boss has tiger arms, a rhinoceros horn transplanted onto his head, two wings attached to his back, one black and one white, gills on his face and multiple scars covering his body from the surgeries. However, since more time has passed from when he received the surgeries, he has slowly been wasting away.

Personality
He likes bananas and had a strict "no killing" code, until one heist went wrong.

Laughter Style
Temp

Overview
Has an advanced skill set that he gained from doing thousands of heists. This was shown as he was able to escape the Tarako Kingdom's prison. However, due to Vice-Admiral Arzen's modifications, he can barely move as his organs and arms have been seriously messed up. But he just said William had surpassed him in his prime when William was level 12. Interestingly, Boss didn't mention this when William was level 8, meaning that in his prime was somewhere in this range.

Six Powers
Boss tried to teach William how to use Geppo many years ago, although he can't use it for long due to his age. William later recalled his teachings and eventually learned to use the technique properly under his tutelage. Boss has also taught William how to use Soru. Since he is able to teach these techniques to others, it can be assumed that he is a proficient user himself.

Haki
Boss is a proficient user of both Armament and Observation Haki, but does not possess the ability to use Conqueror's Haki. However, he does have some knowledge about it. He was the one who taught the Devil's Luck Pirates about Haki and how to use it.

William
Boss raised William and taught him how to be a thief.

Roulette
Boss and Roulette have become very close in the short time they've known each other, Boss has even been so helpful to Roulette that she became his rock during the gang war int he Oasis.

Trevor
Trevor hates Boss as he killed his parents and stole his brother. Boss seems to understand Trevor's feelings and seeks forgiveness.

History
About 28 years ago, he killed Trevor and William's parents and kidnapped William at a young age. Currently Boss is playing cards with and getting very friendly with Roulette.

Trivia

 * Boss is the first character chronologically to use any of the Rokushiki, namely Geppo.
 * It is implied that Boss has the Will of D., as Arzen mentioned that he had "strong blood", the same as William and Trevor.
 * Boss loves pineapple juice, as it is, in fact, the best juice.
 * Boss knows a great doctor, whether that be the previous user of the Ope Ope no Mi, or simply a genius doctor is still undetermined, as he mentioned that he knew someone who could fix his messed up organs in the New World.
 * Boss is the first character confirmed to have access to Observation Haki.

Quotes

 * "Like triple kill me William, like quad kill me."
 * "If you're ever in a situation where you and a lass are going to fall into a pit full of piranhas, I know very specific, remember this trick."
 * "Oh fuck!"
 * "Would that make you the Will of D?"
 * "William, you have to remember, we are not gamblers. We are thieves. We cheat! You have to remember that you wont get far in life if you don't pull a few strings!"
 * "Did I ever give you The Talk?"