Decrepit Vorpal Sword
Legendary Magic Weapon (Long Sword)
This simple long sword is rusty and chipped, the leather around the hilt torn and hanging. Close examination reveals faint elaborate script in Gaelic running the length of the blade.
Property: You sustain a -1 penalty to attack rolls and damage rolls you make with this weapon, due to its degraded nature.
Property [Attuned]: You gain a +1 bonus to attack rolls and damage rolls you make with this weapon, and ignore the -1 penalty. Attacks you make using this weapon ignore resistance to slashing damage. When the number you roll on the d20 for your attack roll using this weapon is 20, make another attack roll against the same target. If you hit again, the target takes an additional 4d8 damage. If the second attack roll is also an unmodified 20 and the target has 100 hit points or fewer, you lop off its head, killing it instantly. If the creature doesn’t have a head, you instead chop the creature in half, with the same lethal result.