- The laboratory in Yetzirah. 'Imperfect' angels are used as living lab-rats and kept awake and conscious constantly to observe their nerve-reactions to all the experimenting.
- Stakers. It's a term used for angels whose brains have been altered and doctored with specific needles to eradicate and avoid 'unnecessary thoughts'. This may also include limiting certain physical actions.
- In the anime, Setsuna gets his arm torn off in slow, graphic detail by a Golem. Thats right, a Golem tore the arm off an angel. Slowly.
- The idea that God doesn't love us and created us only as an experiment.
- The terrifying and deranged Sandalphon and what he does to Lailah.
- Heaven and Hell are just as corrupted and terrible as Earth. Heaven as humans imagined it is a mirage.
- What happens to an angel once its wings get cut off.
Nightmare Fuel / Angel Sanctuary