Never, it’d be a plot hole if he did, it was told that after countless years the belzebub are it’s own power to fill it’s hunger, unless you somehow feed it enormous demon energy enough to fill up a being strong enough to destroy several countries, you can’t add more slots
Avalanche
When Will he unlock another slot in beelsebub
Anti ICE
Never, it’d be a plot hole if he did, it was told that after countless years the belzebub are it’s own power to fill it’s hunger, unless you somehow feed it enormous demon energy enough to fill up a being strong enough to destroy several countries, you can’t add more slots