Verfluchte Zwillingsschwester

The Verfluchte Zwillingsschwester (fair-FLOOKH-tuh TSVIH-leengs-shveh-stur; Ger. "damned" + "twin sister") is a spell used by Hexenbiests to take away a Grimm's powers. It can only be performed by a Hexenbiest who has lost their powers and regained them through the Contaminatio Ritualis. Once the potion is complete, the Hexenbiest responsible places a Witch's hat over the top of the cauldron containing the potion and inhales the vapors of the potion through the top of the hat allowing the Hexenbiest to turn into another person that they have gathered the DNA (ex: hair) from, usually the sexual partner of the Grimm. Then to take the powers from the Grimm, the Hexenbiest in their newly disguised form must have sex with the Grimm. The residue left over from the potion can be used to nullify its effects, but will lose its potency over time. If the Grimm drinks the liquid inside the cauldron before they lose their powers, the spell will be neutralized.

Side Effects
Within a couple days of the spell being completed, the Grimm and the Hexenbiest will both randomly get strong headaches at the same time which allows them to see through the eyes of the other for a brief amount of time.

Reversing the Spell
To reverse the Verfluchte Zwillingsschwester effects, the Grimm who lost their powers must have sex with person the Hexenbiest disguised themselves as to take the Grimm's powers after that person has inhaled the potion to transform themselves into the appearance of the Hexenbiest.

Reversal Side Effects
After a Grimm completes the process of getting their powers back, the person they had sex with to get their powers back may suffer stomach and head pains, resulting in them turning into a Hexenbiest.

Recipe
Im Hexentopf soll es sieden.

Und Dir ein neues Ich beschieden.

Sumpfger Schlange Schwanz und Kopf.

Brat und koch im Zaubertopf.

Molchesaug und Unkenzehe,

Hundezung und Hirn der Krähe;

Zäher Saft des Bilsenkrauts

Eidechsenbein und Flaum vom Kauz.

Ein Opferhaar sollst du dann pflücken,

Dich so mit 'm Spiegelbild beglücken.

Den Topf dann mit dem Hut bedecken,

Um das Gebräu wohl auszuhecken.

Starken Zauber eingemischt,

Höllenbrei im Kessel zischt.

Translation:

In a cauldron it should boil.

And give you a new self.

A swampy snake's tail and head,

fry and cook in the magic pot.

Newt eye and toe of a toad,

tongue of a dog and brain of a crow;

Sticky juice of henbane,

a lizards leg and downy feather of an owl.

Now pick a victims hair,

it will rejoice you with a mirror image.

Cover the cauldron with a hat,

to concoct the brew.

Powerful magic mixed in,

hellish pulp sizzling in the pot.