I Accidentally Became The Dungeon Master, Oops
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At the end, we decided to Summon anything for now, if we ever have a shortage of food, we'll summon something from afar and then use [Summon] to bring it to me anywhere I am. This way we can produce meat in the dungeon easily. Of course, I have to give it a sizable amount of Mana. I am pretty sure that once it surpasses its maximum capacity of 1000000 it might Rank Up and grow bigger, which might make stronger monsters available.
But for now, I'll simply use the dungeon as a meat dispenser while I accumulate Mana into it daily. And as for the treasures it can create? Nothing too special, they're hard to create into treasure chests because this dungeon can only make a few very low-quality potions out of them, it can't create gold or precious gems yet either, sometimes, a rusty iron sword or a set of rusty armor… I guess for a newbie adventurer that would be good enough.