Brains to Mush

You cast this spell on one creature you can see. They must make an intelligence saving throw. If they fail, their effective intelligence score (not modifier) is reduced by your spellcasting modifier. This can be removed with anything that can remove a curse (since it is one). This spell does not stack with itself.

You can cast it at a higher level. For each level above the 2nd level, you can target an additional creature. At level 9 you may instead target an area. The interpretation of "area" is up to the DM.