YMMV / Beneath The Sun's Surface

• Nightmare Fuel: Holy crap, the things that Celestia goes through in this is terrible, the gore is not Cupcakes level, but is the torture, her screams and ultimately her Despair Event Horizon that makes this story really terrifying.
• The Woobie: Princess Celestia is one big woobie in this story, the physical torture breaks her; the pain, the agony and the despair that she goes through is a magnet for nightmares. Even after she escapes, she still suffers nightmares where she's torture by her own sister. She thankfully managed to recover from the experience.

---