Rod of Nim

Rod, very rare (requires attunement by a wizard)

This dark silver scepter radiates with psychic energy. While holding it, you can change the damage type of any spell you cast to psychic damage.

You can use a bonus action to activate the rod, at which time it begins to pulse with power. The rod deactivates after 1 minute or if you deactivate it early using a bonus action. When the rod is activated, and then again as a bonus action for the duration, you can force a creature that you can see within 60 feet of you to make an Intelligence saving throw against your spell save DC (a creature can choose to fail the save). On a failed save, roll a d6. That creature takes a penalty equal to the number rolled to any ability check, attack roll, or saving throw it makes using Intelligence, up to a maximum cumulative penalty of −6. The rod then gains a number of charges equal to the amount the penalty was increased by; it can have a maximum of 10 charges at a time. When the rod deactivates, it loses any remaining charges, the effects of any spells cast by the rod end, and all affected creatures no longer have a penalty to the associated rolls.

Spells. You can use an action to expend 1 or more of the rod's charges to cast one of the following spells from it, using your spell save DC and spell attack bonus: charm person (1 charge), confusion (4 charges), inflict wounds (3 charges; 3rd-level version; psychic damage instead of necrotic), mind blank (2 charges), or power word stun (8 charges). Any saving throw required by a spell cast in this way is an Intelligence saving throw, instead of its normal type.

Curse. This rod is cursed, and becoming attuned to it extends the curse to you. While cursed in this way, you're automatically stunned until the end of your next turn whenever you fail an Intelligence saving throw. While the rod is activated, you also have disadvantage on Intelligence checks and Intelligence saving throws.

The old mage's tower had been a grim gauntlet; the lure of its lost knowledge was—by now—barely enough to draw the young wizard onward, ever higher. With each trial his exhaustion grew, and he could feel his mind slip further away from him with every step. From his sharpness as an Orostead graduate, he languished in his current stupor. Worse still, his vision flashed with sparks of scarlet and pink, but when he turned to find their source, all that remained was a ripple in the air and a hole in his thoughts.

So when he reached the tower's zenith, he could barely muster the coherence to be shocked. Instead of an empty ruin, the highest chamber held the old mage himself, now a stately lich. His withered hands rested on a deep silver scepter, which lit their smile in familiar hues of flickering purple and red.

"The taste of your mind has been a rare treat in these quiet days," he cackled, "I am only sorry you won't be savoring it yourself. A hale mind is too great a threat to my secrecy. Your efforts shall, at least, be remembered by me."

And the last bastions of the wizard's conscious mind collapsed.