Spirits were beings that were extremely sensitive to any kind of energy fluctuation, mostly because they could interact with energy directly with their souls! This was very crucial information to keep in mind when designing a room for them. But the question was… how was Lex supposed to actually use it?
The first thing he did was use the feature of the meditation room to gather spiritual energy and multiplied its effectiveness. But was just raising the concentration of energy enough? That was unlikely, or else spirits would all just congregate in areas of high energy concentration. No, there had to be something more. Something soothing. Something warm and comfortable. Something like… a hot tub!