Inflictors are elves with the ability to inflict pain or other negative emotions on someone else, including elves and goblins. Sophie, however, can also inflict positive emotions, thanks to her alicorn inspired DNA. This ability has the capability to incapacitate others and is very rare. Because this ability can be dangerous, the Council monitors Inflictors carefully.
Sophie describes seeing colors in her peripheral vision before she used this ability. Bronte taught Sophie to imagine all her strong emotions tied into a knot so when she needs to use infliction, she can unleash more power.
Sophie discovers this ability in the first book when she is with Dex in Paris. In a different book, she learns that she can inflict positive emotions as well as negative emotions because of her alicorn-inspired DNA.