Witch/20th
From Legends of Hyrule
Masterful Learning
At 20th level, you become a library of knowledge and a pinnacle of magical research. From now on, when casting a spell you have learned with your Adaptive Magic feature, you do not need to expend extra magic points (or a higher level spell slot) to do so. At this level you also learn any one spell of 11-points (8th level) or lower from any class's spell list and cast it as if it was a researcher spell.
You also have advantage on all Intelligence (Medicine) checks and all Intelligence saving throws from now on.
You can always accurately remember any text or scripts you have read since you acquired this feature, even if it was from a language you didn't understand.