Vorpal Longsword, Jess the Beheader edition

This weapon (1d8 damage or 1d10 damage with two-handed strikes) grants a +3 bonus to attack and damage rolls, and ignores resistances to slashing damage. Additionally, any critical hit rolls result in a trademark “Jess the Beheading”; if this happens to a creature that cannot survive without the lost head, it dies horribly. Slashing damage-immune enemies, headless enemies, legendary enemies, or enemies with neck diameters that exceed the length of the longsword are not beheaded, but the above will instead take extra 6d8 slashing damage.

Because this weapon is indeed made from the finest regional silver, there are likely additional applications for this blade; as an example, double damage for any creatures that abhor contact with silver.