Your name is Cayde, and you don't know how you got here.
The Ruins have changed, the creature that was caring for you has vanished, and you stand, alone, in the pale light of an absent moon. A sense of deja-vu washes over you, so strong it almost hurts when you try to wrap your head around what you're seeing.
You stand in the hallway outside your room, ankle deep in dust. Your hand finds the cannon on your hip, and you clutch the grip tightly, seeking reassurance. You only find doubt. Whatever has brought you here, you know it most likely doesn't fear your sidearm.
"Hello?" you call out hesitantly, hoping to hear Toriel's voice call back, but it doesn't. Instead, a faint whisper disturbs the quiet. A child's voice, by the sound of it, directly behind you. You draw and turn, only to see a faint puff of ash. Then another. And another.
They're leading away from you, towards the living room and kitchen. Like footsteps. You consider firing at where the being would be, but ultimately decide against it. Six shots, after all. Best not waste something in such short supply.
Instead, you give chase, careful not to slip on the dust as you do so. The footsteps lead you to a staircase, then down into the basement. Toriel told me pretty clearly not to come down here. That it wasn't safe. But...she's not here. And I don't know where "here" even is.
You follow, noting that, while there are torches and candles to light your way, none bear any fire. The eerie glow from upstairs continues here, casting no shadow and having no source. Almost as if the air itself were glowing.
You walk carefully down the hallway, hand wrapped tightly around the handle of your prize. When you reach the end, the great stone doorway sealed shut by time and piled up ash, you hear the strange whispers again, and again, you draw and turn.
For a split second, you think you're looking into a void. Something dark and awful in human form, a three-dimensional shadow glaring at you just twelve feet from where you stand. But before you can believe what you are seeing, the world just...pops. You stare at a child not much older than you, wearing a blue and purple sweatshirt.
Your back to the door, you realize you were tricked.
"Who are you?" you ask calmly. "What is this place?"
"The dream," they say absently. "I am Frisk. The Demon that comes when their name is called."
"I didn't call you."
"I'm not here for you. I'm here for the one eavesdropping on us."
"Then go bother them. Leave me out of this. Send me back to the real Ruins. Back to Toriel."
"I'm afraid I can't." Frisk flicks their wrist, and four crimson daggers materialize around her head. "You are needed, Soul of Justice."
The daggers fly towards you, and your left hand finds the hammer of your cannon. Four shots echo loudly in the tunnel, slamming into your eardrums so hard the world rings. Frisk says something you can't hear while you watch the magic knives shatter under your gunfire.
They draw another knife, real, this time, and stalk towards you slowly. Your aim turns away from the shattered magic and onto them directly. You shout at them to back up. They refuse, and you fire.
Frisk vanishes in another puff of dust, and you hear, just behind you, the sound of something heavy landing in ash. On pure reflex, you pull the hammer back and fire under your arm. The shriek is all you need to know you've struck them, but before you can turn to finish your work, you see the shards of magic begin to vibrate. The daggers reform, ichor dripping out of the cracks. Your hand finds the speed-loader in your front pocket, but it's too late.
The daggers descend upon you, and you, Chara, wake, your fingers still clutching leather and iron.
The gun is still in your hands, and it's levelled at Sans' chest.