Ah, well… [ Please don’t make him explain D&D while they’re in the middle of a death forest. ]

“Mana” is a phrase that kind of popped up in fiction, and it’s exactly as you described it, a pool of power that spellcasters draw from. In reality, have no such thing, but I guess the trade off is that all of our spells are written, and that takes time. It didn’t occur to me that there might be people out there who actually have mana.