To get Bisento in King Legacy, you must defeat the boss Quake Woman (Level 1925) at War Island in the First Sea. While the quest to defeat Quake Woman has a level requirement of 1925, there is no requirement to fight the boss and obtain the drop. Bisento is an Epic Sword/Halberd, so its drop rate should be around 1%. It is inspired by Whitebeard's Halberd in One Piece.
Bisento is one of the mid to low tier swords in King Legacy, but it remains one of the best swords you can get in the First Sea. Bisento is a great option that you may use for quite a while in King Legacy.
Its M1 attack speed is slow, and it deals 4,726 damage with Armament Haki V1. Bisento is not recommended in PvP as both skills deal a single blow. Their damage is quite heavy, and they are both easy to use, so it's a good sword/axe to use in PvE, while Quake Smack temporarily sends enemies inside its AoE airborne.
Its Z key move, “Quake Smack” is unlocked at 100 Sword Stat Points, and it deals 9,475 damage with Armament Haki in a single blow. It's range is quite short as the smack hits the area surrounding your character, but it causes enemies to go airborne.
Its X key move, “Quake Ball” is unlocked at 300 Sword Stat Points, and it deals one hit for 11,275 damage with Armament Haki. It's very easy to aim and it has a very long range.
Note that you must have Armament Haki enabled for both Skills to work on Logia users.