The Fungus Lord's digestion process was a bit faster than Ybur had anticipated—it had omitted the fact that, as it increased in size, its eating and digestive abilities were also rising correspondingly.
However, as its body rapidly expanded, Ybur suddenly realized a problem.
It was originally preparing to perform the Awakened's ritual for Perfection of body and mind. But the Ritual required certain preparations before its commencement, including fasting, abstaining from drinking, and sleep deprivation. This was mainly to make the participants fall into a state of weakness and hunger, since in the philosophy of the Path of Perfection, when a person's flesh and mind both become frail, their true "essence" would then stand out.
But speaking of hunger...
Slimes are different from humanoid creatures; when a slime gets hungry, it digests itself. Its massive body in itself is like a reserve of food.