Beheading Blade

Weapon (whip), legendary (requires attunement)

This sinister chain-whip is decorated with the scowling face of a fire yai oni and connected to a wicked, black chain via a detachable hook, functions identically to a vorpal sword that scores a critical hit on a roll of 19 or 20 (though it beheads a target only on a natural 20). In addition, when the wielder makes an attack with a beheading blade, the wielder can use a bonus action to unhook the slashing blades from its chain in order to launch the weapon at one target within 60 feet, functioning as an attack made with a thrown weapon. When attacking with a beheading blade in this manner, the wielder uses their Strength modifier instead of their Dexterity modifier on their attack roll. The slashing blades fly back and reattach themselves to the beheading blade at the end of your turn. While the head is detached, the beheading blade can be wielded as a +1 whip with no other special abilities.

A monk or other wielder with ki points can expend 1 ki point can use a bonus action to toss the beheading blade into the air and command it to attack on its own for 1 round, as a dancing sword. The wielder can keep the beheading blade dancing and attacking for up to 4 rounds by spending 1 additional ki point and a bonus action each round. After the wielder stops spending ki, the beheading blade returns to its wielder, as normal for a returning weapon.