Amayon must surrender a vast quantity of souls to pass back down to Sheol, and his weakened regional spell targets all souls in Cuba.
Even a demon prince cannot return to Sheol without paying for passage. Amayon's power makes his required tithe exceptionally large despite the weakness imposed by his current shell.
His wide-area spell is calibrated to inhale all souls within Cuba, barely enough to send him home. The spell's necessary area grows with his power, which is why Carl intends to free and strengthen him rather than stop the casting.
A red river-like portal demanding a scale of countless souls before a chained demon prince.
The tithe links Amayon's strength to portal range and makes Carl's global amplification possible.