However, that's boring.
And they are like right next to an unclimbable mountain, which is not boring. And she never actually said she'd stay by the camp, they just assumed it. And she knows how to climb things! Safely, even! Nothing can go wrong with this plan. Up the mountain she goes.
Things that are less fun: falling into a massive sinkhole. That's not very fun. On the other hand, she lands on... a bed of flowers? A pile of enough bright golden flower petals, thick enough to completely break a fall of what must have been a hundred feet.
It's dark down here.
This is not what was supposed to happen!
Wincing, she sits up and opens her groundsense.
And there's something, large quantities of something. Energy. Raw power, floating around and filtering through itself and... creatures? And a shell of it, brighter than the sun, woven into a vast prison around what must be the whole mountain. It must have been hidden from the outside, imperceptible to groundsense, for anyone to have missed this for so long.
And there's something, its ground wrong in an intensely distressing and almost familiar way, moving through the earth toward her.
Sable shrieks. She doesn't have a knife, why doesn't she just carry one at all times like Father...
It bursts through the loamy soil. It's...
a flower. With a little face, one that somehow manages to be cute instead of plummeting into the Uncanny Valley. Its petals are glossy gold, just like the ones beneath her, but this one's seem almost to gleam with inner light.
"You're new to the Underground, aren't you? Goodness, you must be so-"
It stares at her, seemingly recognizing someone in her eyes. "Chara?"
What. What the blight is this - talking flower with a not-quite-malicelike ground? How? What?
What are her options here. Her options don't look great, to be honest.
"...very helpful, thank you."
She tries... moving the thing around. Such as for example back into her body, that seems like a good place for it to be.
"Well, you want to become strong, don't you? Everyone wants to become strong. But right now you're weak. Your soul's fragile and dull. I can help it to grow stronger by giving you some Love! Down here, Love is shared through these..." He waves a frond, and several glowing orbs appear around him. "Little white... 'friendliness pellets.'"
They float towards her soul lazily. "Try to catch them all!"
Sable has never been more tempted to ground-rip an arguably living being in all twelve years of her life.
But no matter how desperately suspicious the creature, she has no way of getting her apparently vitally important soul back without playing its horrible game.
So she braces herself and bonks the heart gently against a pellet.
The collision before felt bad.
This feels like a blunt, serrated, rusty knife being driven through her spine. She's left hanging on to life by her teeth and nails.
Flowey's adorable little face twists into a hideous grin. "You IDIOT. Did you really think someone would help you, down here? In this world it's kill or be killed."
In the distance, there's the sound of paws running towards her. Flowey looks to be too busy cackling to notice.
She reaches out with groundsense and takes hold of this horrible little creature's horrible little life-essence and pulls as hard as she can. Which is very.
And the owner of the paws careens into the room.
She looks like something between a woman and a goat and a very sleek bear, and she is enormous. Sable's father standing next to her would look shorter than Sable herself looks standing next to him. And, incidentally, her paw-hand cups a magnesium-bright ball of fire.
The fire dissipates when she sees Sable. "I thought I heard-"
She stops in her tracks. Her eyes go distant. "Chara?"
"Who the blight is Chara?!" gasps Sable. She feels less like death now that the flower-thing's brilliant ground is being absorbed into her own, but this restorative comes with its own complications, namely an all-consuming agony as her damaged ground fails to reconcile with the foreign material.
"I-"
She shakes her head. "My adoptive daughter. She died. You look like her. Sorry."
She looks sharply at Sable's soul. "Who did this," she snarls, and makes a complex motion with her hands.
Energy suffuses Sable, mending her spiritual wounds and brightening her soul until it shines again. Her ground feels soothed.