Dark Energy: The origin of dark energy dates back to before 'Darkness' of any kind was formed. The first 'versions' of it were a product of negative human emotions and it was enough to corrupt plants and small creatures. It was only after the souls of the dead power holders joined in that it started corrupting larger, more powerful creatures. It even started affecting magic, making it weaker. The only thing that stands against it is the Seasonal Abilities. We're quite sure it's because of the power holder souls.

Alchemy: Scholars at the City of Lost Memories practice alchemy. It's potion making as we know it has taken its inspiration from alchemy, but has left out significant parts of it such as [messed up text unable to read at all, goes on for a long time]. Practicing such things outside the city is very dangerous and forbidden.