You were a god.
There was limitless potential to what you could do.
At first, you had hoped for a happy ending for the universe. Any monster that threatened you or raised a proverbial fist to block your progress was met with the unending kindness of a saint. If they threw balls of magic at your soul, you merely sidestepped and offered them a compliment or a pat on the back. If they threw spears or obstacles in your way, you patiently offered your mercy until they relented. It didn't matter who challenged you. No one else could rival the blazing innocence and compassion you held and inspired.
Your efforts paid off when at long last, you saw the sun again on the surface. A hard-earned victory that had required understanding. You felt the presence of your friends surrounding you, adding warmth to your heart. Everyone had achieved the happiest ending through your efforts. This was how it should be; this was the way things were meant to play out.
But a little voice in your mind offered the question that continued long after the happy ending:
But what if it happened another way?
And so you reset the world and began a new journey. This time, you decided, you would play the scenario differently. In some runs, you killed off one monster at a time, wondering how its death would shape the ending. No one seemed to notice, not even when you decided to go for the boss monsters - except that one skeleton. Sans.
He held mysterious, depthless eyes; on some days, he wore a warm smile that spread across his entire skull and radiated friendliness. On others, those pits of darkness made you shrink back. The judgment was there, whether or not he was vocal about it. And yet, it intrigued you. This skeleton had been but a part of the story, another variable in the long stream of personalities. Now, he was the gatekeeper, your judge of your past deeds. You wondered, how would he react if things changed more dramatically?
And so you reset. Slowly, you added more monsters to the list of kills and watched your LV rise. How would he react knowing Undyne was murdered by your hands? You wanted to know the reactions of all the bit players. Would Undyne change her mind and come for your head if she found out it was you who plunged the knife into Alphys' back? Would the King of Monsters order for your heart on a silver platter if he found out Toriel wasn't even alive anymore? What would the town of Snowdin do if all the Royal Guard members disappeared without a trace? It wasn't like they could tell your hands were covered in sin. Well, except your judge.
The reaction was nearly identical every time; the outcome was different, if only by a margin. Some endings were a mutual separation while in others, Sans would point-blank tell you to stay the hell away from the Underground. It didn't really matter what he thought in those times. The story had already concluded and you had given up interest.
So the world began anew.
In past happenings, you had always spared the lovable and soft-hearted Papyrus who didn't have a mean bone in his body (literally). However, as you thought on it, you knew how attached Sans was to his brother. Would his death bring about a change?
You weren't disappointed.
Sans was unforgiving of your actions, even if you had spared every last living creature except his brother. You were nothing more than a dirty brother killer in his eyes. The satisfaction blossomed in your heart. Here was the game changer. You grinned.
What would he say if every single resident of the Underground met their end by your blade?
Curiosity got the better of you; the world reset and from the beginning you were relentless. The monsters begged and pleaded for you to stay your hand but you hardly twitched a finger. If they were praying for mercy, there would be none. Kill or be killed? It was be killed for them, since any death on your part was immediately swept under the rug for a reload. Failure was not an option. When it came to Papyrus, you had to quell the wavering of your soul to deal him the single blow; chopped to smiling bits, indeed.
When you arrived at the judgment hall, there he was. Instantly you knew, you had crossed a line. His speech, his mannerisms were different. Your judge had turned executioner. Faintly you thought you had brought yourself to a sudden and damning end, but through determination, you defeated the boss who had appeared on first account to be unbeatable. You manipulated the battle to your success because you had control; Sans could do nothing against your power, not even when he broke the rules himself. But, despite the trials and tribulations you faced to arrive at the end, you were unsatisfied.
And so you reset the world again.
They were all nothing more than your playthings. It was all just a game, a way to pass the time. You were above the consequences of your actions - because you could always wipe the slate clean and start fresh. This world rested in your fingertips.
You were a god.