Tortles have a Dex-based chance of avoiding getting decapitated by ducking their head back into their shell.

If the hero gets decapitated, they don’t die, but their head falls into their inventory. Thereafter, they are permanently blind unless wielding the head in the offhand slot.

A chaotic artifact axe (or battle-axe, not specified) The Executioner’s Axe: has a small chance of beheading on every successful hit like Vorpal Blade.

Wielding Vorpal Blade in your offhand will never decapitate monsters; instead hits that would have decapitated will instead sever a limb, which can make the monster lose its weapon or permanently lose a claw attack.

Invoking Vorpal Blade gives some sort of message about its keen edge gleaming, indicating that its next hit will have a high critical ratio (perhaps 10% instead of 5%) for increased chance of decapitation.

New object, a metal collar you wear on your neck. Makes you immune to being decapitated by Vorpal Blade. It would probably be worn in the amulet slot.