When you equip a ring of hunger or conflict (or regeneration), you get a message about feeling hungrier.

Non-cursed rings of hunger don’t drain excess nutrition when you are Hungry, and slow digestion rings don’t slow your digestion when you’re oversatiated.

Merge the rings of slow digestion and hunger into a single chargeable ring of digestion. Negative values increase hunger faster, positive values slow it down. Duplicating the effect of a vanilla ring of slow digestion would require getting a +10 ring or stacking up to 10 with two rings. (Possibly the negative/positive values should be switched, but that would complicate the generation code.)

The hunger property, instead of doubling hunger rate, halves any nutrition you get from any source, making it marginally more useful for eating large corpses. (This should probably only be granted by the actual hunger intrinsic, i.e. the ring of hunger, as opposed to other intrinsics like conflict and regeneration that burn through nutrition fast but aren’t explicitly about being hungry.)

You can invoke a ring of hunger to make yourself more hungry immediately so you can eat dragon or giant corpses. (You have to be wearing it and have it identified.)

Maybe rather than having all rings of hunger capable of doing this, have it be a single artifact ring of hunger. Suggested names for this artifact include Overeater, Bottomless Pit, Cookie Monster, Glutton, and The Hungering.