I know there is already a similar question, but it doesn't really give me an answer. Is there such a thing as a feat or an item that causes enemies to make saving throws like wisdom or general saving throws with disadvantage?
I wanted to create a mage (don't know which class yet) who specializes in CC and spells like Phantasmal Killer, but I don't feel like a high spellcasting mod would really be sufficient to make the CC more reliable.
edit: Based on comments and uncertainties, I would like to say that all ways to increase the likelihood that the spells will apply its effect are helpful. It doesn't have to be a disadvantage. It can also be an effect that increases my spell mod or decreases enemy saveroll as long as it can be used with a mageclass.