Dark-side reservoir

The dark-side reservoir was a wellspring of evil energy emanating from the many Sith crystals and artifacts that Darth Sidious kept in the Grand Republic Medical Facility. At the center of the reservoir hung a massive Sith-imbued kyber crystal, slivers from which were be used in Sith lightsabers. When Anakin Skywalker was reconstructed into Darth Vader following his duel on Mustafar, his recovery was aided by an "immersion" in that wellspring.