Editing Sword of Sharpness (section)

===Details===
Weapon (longsword), very rare (requires attunement)

When you attack an '''object''' with this magic sword and hit, maximize your weapon damage dice against the target.

When you attack a '''creature''' with this weapon and roll a '''20''' on the attack roll, that target takes an extra '''14''' slashing damage. ''Then roll another d20.'' 
If you roll a '''20''' on this second roll, you lop off one of the target's limbs, with the effect of such loss determined by the GM, and ''then roll another d20.'' If the creature has no limb to sever, you lop off a portion of its body instead.
If you roll a '''20''' on this third roll, then you lop off the target's head, killing the creature instantly (unless the creature doesn't need its head to survive :-).  In the absence of a head, the DM will determine the effect. 

In addition, you can speak the sword's command word to cause the blade to shed bright light in a 10-foot radius and dim light for an additional 10 feet. Speaking the command word again or sheathing the sword puts out the light.

Proficiency with a longsword allows you to add your proficiency bonus to the attack roll for any attack you make with it.