A Spiritual Host typically has only one Spirit Body, as their method for gaining strength is far too unnatural. It's not that Deities haven't considered giving a Spiritual Host multiple Spirit Bodies, but for all their power, Deities lack the formidable research capabilities of Wizards.
Having multiple Spirit Bodies in one vessel would only cause the Spiritual Host's power to swell uncontrollably until they burst like a balloon!
Even Wizards spent a great deal of time solving this issue. But now, though a solution exists, they face an even greater problem: you can't make bricks without straw...
According to the insane experiments conducted by Mad Witches in the past, a single body hosting multiple spirits only occurs under two conditions. The first is a matter of pure luck—it just happens, with no discernible pattern or control.
The second method is controllable, but that's not necessarily a good thing.
