@askgerror liked for a starter
With multiple timelines you will always have a variety of outcomes, so having one with the human child killing all the residence of Waterfall, and a few in Snowdin was seemingly typical. They might of killed more hadn't they entered the bar, the child came in to potentially steal money or grab some monster food for their HP, that was his guess. Yet standing in their way was Grillby, who paused as he stood in the middle of the room. Flight or fight responses kicked in, and with how he was emotionally, Grillby was more inclined to fight the human. He had already lost so much, he had nothing to lose at this point.
The battle itself was intense, it left Grillby weakened by the end as his HP dropped just shy of becoming one. In front of him laid the biggest monster in the underground, though what concerned him was the lack of a soul. He didn't remember it shattering with any of his attacks, just that the human fell, and stayed down. Morbid curiosity made him start his staggering over to them, to make sure they truly were dead. Upon checking them, he found what he expected, their HP was at zero. Slowly he staggered back to his bar to restore some HP, before grabbing an umbrella to head to Waterfall. He couldn't get to Hot land from Snowdin as it was reported the River person was slain, their boat found beached in Waterfall. Honestly, at this point Grillby felt the walk was pointless as the human was dead, but everyone on his phone's contacts were dead.
With that, he was off. With the memory of a fight that was never supposed to of happen as it unintentionally caused the human's soul to glitch, and not release from their body.
