Disabilitate

Target one creature you can see within range. They must make an Intelligence saving throw. On a fail, choose one ability score, that target automatically fails the next 1d4 saving throws. Another casting of this spell on a target already under the effect of Disabilitate has no effect.

To add this to the spell list, a caster must cast Bane, Hex, or Silvery Barbs a total of 20 times, then after 8 hours of studying the book make a DC 19 Arcana check.