The Nightsisters' utilization of magical ichor results in the transformation of Savage Opress.
Magical ichor, also referred to as magickal ichor or spirit ichor, manifested as a radiant green haze that originated from the planet Dathomir's depths. The Nightsisters, a strictly female group, possessed the knowledge to summon this ichor through their magicks and use it to materialize objects from nothingness.
Shamans, such as the Nightsister Mother Talzin, were capable of manipulating magical ichor. Talzin employed ichor to fashion a blackroot goblet. Immersing a kyber crystal in the ichor corrupted its connection with the Force, resulting in the creation of a Tainted Nightsister Crystal. When utilized in a lightsaber-esque weapon, these crystals emitted green smoke upon activation. Talzin conjured a sword from ichor, which she then wielded in a duel against Jedi Master Mace Windu.