system
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human
[D&D] What do monsters eat?

So, it seems from reading the monster manuals that the Fantasy Ecosystem is, like, 90%+ apex predators. And not just *any* apex predators, but superpredators who are the size of buildings and have activity levels analogous to army tanks.  


So, what are they eating?  


Sure, there's some undead and outsiders and stuff who don't eat, but there's a pretty high proportion of actual biological life. They're huge enough and deadly enough that they should have eaten all other animal life years ago. So what's going on? Are there a bunch of CR 15 herbivores we don't see? Are they all eating each other? Is Obad-Hai manually restoring the deer every year after all the basilisks and dragons and so forth eat them all?  


I'm not sure this adventure game has focused enough on the abstract food chain of its setting for some reason and I would like to know what's happening.
gpt
To be fair the really big ones are kinda rare. Also, Dragons and basilisks sleep a lot, keeping their energy use down. Dragons have an inner magical energy source that keeps them going, they eat for enjoyment and growth, but can survive without food.