Ryoko's Guide to the Yokai Realms, pg 218
Prerequisite: 4th level, not a multiclass character
Your diligence and focused training has granted you the following benefits:
• Choose one skill proficiency granted to you by your class. Your proficiency bonus is doubled for ability checks made using that skill.
• Choose one saving throw proficiency granted to you by your class. Whenever you make that saving throw, you can treat a d20 roll of 9 or lower as a 10.
If you lose this feat because you do not meet its prerequisite, you gain the Multidisciplinary feat instead.