White Mustache

Appearance
White Mustache is Whitebeard or also known as Edward Newgate from the One Piece anime, the name is changed so there isn't a copyright strike.

Information
The boss has a massive heath pool and does large amounts of damage, a team is required, he uses the skills of Bisento not the fruit itself.

How to summon
You need a mysterious key that you get from monkeys (1% drop) that are located at the island where haki trainer is, when you have it, go to prison and place the key inside the keyhole by equipping it and jumping against it (it's sometimes hard to get it in), boss respawns after 1 hour and you need to do everything again.

Teamplay
If you go with a team it is required to turn off haki so you don't damage your teammates (if they have a logia fruit, see all the fruits here).

Solo
If you choose to do this solo, while not recommended, all you need to do is run and spam ranged moves, you will lose 1/3 of your HP 100% if you even try getting close, fruits with stun & AoE like Goro Goro no mi or Hie Hie no mi are recommended.