Thanks to u/Warpmind for bringing this to my attention.

What the hell is flensing

“Flensing” is the removal of the outer layer of blubber from whales, separating it from the meat of the animal. This was an important step in the process of rendering whales for oil (used in lamp, machine lubrication, etc.).

For what it’s worth, whaling as an industry is a really evocative historical practice to use as inspiration for your games. The imagery of a huge creature being murdered and broken down for parts combined with the industrialized bloodbath that grew from the profit motive makes a great source of economic, political, and moral tension.

Flensing in D&D

Flensing is a spell from 2e/3e used by the Red Wizards of Thay as a form of torture.

Over four rounds, the victim’s flesh is torn and disfigured, permanently reducing their Charisma. It requires an onion from a field plowed by a rothé as a material component. As the victim’s skin is peeled gradually over the course of the spell, so are the layers of the onion.

Victims of this spell often give in during the first round of casting and tell the Red Wizards what they want to know. On occasion, the wizards let the spell complete its work even after they have gotten the information.

Flensing for 5e

Flensing

Level 7 Necromancy
Casting Time: 10 minutes
Range: 10 feet
Components: V, S, M (an onion from a field plowed by a rothé, which the spell consumes)
Duration: Concentration, up to 1 minute

The skin of a creature within range begins to rip and peel.

On each of your subsequent turns, you can take an Action to deal 2d6 necrotic damage to the target automatically. The target must make a Constitution saving throw.

On a failed save, the target’s Charisma score is permanently reduced by 1. Their Charisma score cannot be reduced below 5 in this way.

The reduction in Charisma can be undone by greater restoration, heal, or wish.

The spell ends if the target is ever outside the spell’s range or if it has Total Cover from you.

This spell was designed to be similar to Feeblemind in terms of power.