Ring of the Sorcerous Adept

Ring, uncommon (2nd), rare (4th), very rare (6th), legendary (8th) (requires attunement by a sorcerer)

This jeweled silver band expands the arcane knowledge of a sorcerer that attunes it. When the wearer observes a sorcerer, wizard, or warlock spell while it is being cast, while its effects are active, or in written form, the wearer can attempt an Intelligence (Arcana) check to teach that spell to the ring, with a DC of 12 + the spell’s level. If successful, the ring stores an echo of that spell.

Once the ring “knows” a spell, the wearer can cast it as one of their Spells Known. If the spell is not on the sorcerer spell list, the wearer can still cast it, treating it as a spell 1 level higher. In addition, the wearer also gains advantage on saving throws against the stored spell. Spell attack rolls with that spell against the wearer have disadvantage.

The ring can store only one spell; if a new spell is stored, it replaces the previous spell. If the ring contains a stored spell when discovered, the wearer must make succeed on an Intelligence (Arcana) check (DC as above) when they attune the ring to discover what spell it contains and be able to cast it.