Starving in the dungeon

Everything get simplified. Everything that's not in the book gets adjudicated. Lots of moving parts that requires extra tables and chart referencing is too much stuff to keep track of. Since your character's survival is predicated on their HP all of the bad shit that you suffer should affect their ability to stay alive and recover from combat.


Eating food is healing
At the end of the day you have to eat food and get some sleep to recover one HD hp. If you don't do both of those things you don't get to recover. It's that simple. If you don't sleep at all you roll with disadvantage on everything until you get sleep. You can go hungry as long as you want, but those hp won't come back til you eat so it's self-regulating. If a PC eats their favorite food they roll with advantage when healing.

In the wilderness you can roll bushcrafting checks to see if you find food, 4 hours per check. This works better if you're familiar with the locality/climate/denizens, or if you're a skilled hunter or tracker. Most of the time bushcrafting stuff is related to Wis. Being skilled gives you bonus points. The less fruitful the clime the harder the check.

Raw meat keeps for about a day or two. Adventurers have pretty hardened stomachs and can survive eating mostly funky stuff. If you cook it it'll keep for a few days. If you find some way to preserve it, like with salt or some kind of mild edible acid, it'll keep indefinitely. If it's definitely rancid the PC will smell it, but everything underground smells rancid.

If you make a meal by combining ingredients everybody eating it gets some +1s to healing based on complexity and deliciousness. Probably it won't be delicious though because you're eating goblins and giant slugs. I'm talking like if someone managed to find or bring something palatable into the dungeon, that normal people eat. Like blood sausage or pickled octopus.

What about in the dungeon?

Finding food underground has to be roleplayed because it's not just lying around like it is in the normal world. If another monster doesn't eat it, the dungeon itself will. You could try eating that slime growing from that drainage pipe. Catch a rat. Gnaw some old bones. Mostly you're gonna have to eat monsters. Hope you brought some cooking gear.

How long does it keep?
The surface levels of the dungeon probably has stuff that's kind of like the stuff in our world and obeys things similar to our rules. It keeps for 1-3 days usually.

The deeper you go the more the rules breakdown. Deep underground reality becomes toxic. Wounds turn septic quickly, diseases spread fast, and everything rots into goo and is consumed by something else within hours, like in a jungle made of hate. By the next day dead things are typically mummified or transformed into putrefied ichor. You have to eat it then and there.

Is this thing gonna make me sick?The answer is probably yes. When eating monsters make a Con or Poison save. If you fail you get sick. Either roll with disadvantage for a while or don't heal your HP or take some stat damage or be completely immobile while you hallucinate and scream and vomit for 2d20 hours. If somebody is a healer of some kind and has access to herbs and can explain what herbs their using and how, they can make a Int check to see if you get better. Then they mark off a use of their herbs.

Disease and mutations
are more or less the same thing to me. The difference is if it's curable or not. Diseases do stat damage and get worse, but probably you'll also get scales or feathers or start rotting or your tongue will turn into a hand and start trying to choke you. Probably worms will crawl out of your anus at night and be so itchy you can't sleep, or your genitals turn black and shriveled, or you'll get a crystallizing rash that spreads. It depends on the thing you eat, whatever that thing is like is what happens to you. You don't turn INTO that thing, but consuming its essence starts having an effect on your DNA. You might be able to cure it by eating more of whatever you ate, but that's probably just be an old wives tale. Maybe your god can hear your prayers all the way down here, and they care enough to listen.

Underground cookbooks
They exist but they're mostly written as jokes by charlatans and taking them seriously could get you killed or worse. Drow don't write cookbooks because drow don't eat food, they have highly trained slaves to brew mixtures of purified essence for aesthetic pleasure, like extractive of the colors a sentient being views as it dies while being tortured, the more subtle and wordless the better. Stuff underground mostly just kills and eats everything it can find without concern for taste. If there are any sources for what's good underground they're written by other adventurers in barely legible script as part of their logs, and can be found on their dead bodies.

Can we get fancy?
You can get as fancy as you want, but it's not going to help your situation. This isn't "Delicious in Dungeon". You're eating stuff that still want you dead even in death. This stuff isn't part of the natural world, there is no food chain or ecology down here. Monsters sprout from each other's nightmares, through rips in aetheric space, or spontaneously generate from mucous touching ashes or septic neck wounds. You're ingesting pure cardinal sin, ire, hate, greed, and venom. It tastes and smells like sewage, turns into a hard knot that blocks your intestines, and your body has no idea what to do with it. Its chemistry is not even of this world.

What about cannibalism?
Probably your safest bet, really. Stuff from your world isn't inherently toxic. You might go crazy eating people though. Veins of the Earth handles this nicely.

I didn't bring a cookpot... Can I hollow out this huge skull and brew soup in that?Now you're thinking like an adventurer! You just earned a +1 on your Con save to see if that beholder brain soup shreds your mind into pieces.

The moral of the story is bring food. Bring lots of food. But food is heavy. Next I'll talk about encumbrance.