I'm working with trolls who are beings made of stone. Troll species/races can range in size from small (3-4ft) to gigantic (hundreds of feet tall--big enough that they're no longer mobile and must be fed by others), but are typically in the 7 - 14ft range.
For all species/races the troll diet consists primarily of meat and metal, but they'll also eat fibers and plastics.
I can see the metal providing minerals/nutrients they need to support their bodily functions, but I'm lost on how meat would be a benefit to them; same thing with fibers and plastic.
How could they support themselves on this diet? If they couldn't, what would a more realistic one look like?