Quartz
Hero
Was musing on this - I recall a feature of sme online games is finding potions that restore mana. Has anyone seen any written for D&D (any edition) that restore spell slots of points?
Not exactly what you're after but in a previous edition there was Mordenkainen's Lucubration which allowed the recovery of one spell of lower level. IIRC it was a 9th level spell. Pushing that into 5E you might make it a 9th level spell that recovers 1 slot of 6th level or lower (depending upon what your maximum is). The lower level cap is because of the added flexibility of 5E. Then you could put it into an item and give it to the PC. (The point of this spell in 5E is not to be memorised for adventuring but to be used in the creation of items.)