Looks like Chloe is full of heart demons. If she had put on the One Ring, it would have taken over immediately. But it looks like her use of an evil grimoire as a shortcut for power is also not a good choice.
Seriously, wtf. Unique magic requires studying rune language, no one’s going to be creating unique magic mid battle. There should have been a 6-12 year old warning, so I didn’t have to waste my time on this slop.