Magic. An ability to do anything via usage of mana.
"Ahhhh, what to dooooooo," I complained to no one.
The library was empty, no one besides me.
"Magic can do anything huh? If so can it make me more powerful? How would I do that? With a system, like from an rpg or… no that could work."
What to power it? A small perpetual motion machine should do. If I make it put power into growing itself… yes, that could work.
What to make it's interface like? How it looks in every story, a semi tranparent display shows up when you say "status". Nah, let's change that. First, it opens to "menu". It's gonna have an attributes menu, with things like stamina and max mana, a skills menu, and a quest menu!
"Wait, how should quests be made? I could have spare power go to making quests, and put a Mana Intelligence in charge of that!"
Once I had designed everything, I began to estimate the mana cost.
"Even to make the PMM, I need triple my max mana. Thank you mom, this mana storage stone truly is coming in handy."
As I went to my dorm room, I put my mana into the stone, and went to bed.