Source: Waterdeep - Dragon Heist

Staff, legendary (requires attunement by the Blackstaff heir, who must be a wizard)

The Blackstaff is a sentient, rune-carved staff set with thin silver veins. It is the symbol of office for the Blackstaff, the highest ranking wizard in Waterdeep. As the rightful owner of the Blackstaff, Vajra Safahr is the only one who can become attuned to it. The staff can, however, choose a new owner (see "Personality" below).

The Blackstaff has the magical properties of a staff of power in addition to the following properties.

Animate Walking Statues. You can expend 1 or more of the staff's charges as an action to animate or deactivate one or more of the walking statues of Waterdeep. You must be in the city to use this property, and you can animate or deactivate one statue for each charge expended. An animated statue obeys the telepathic commands of Khelben Arunsun's spirit, which is trapped inside the staff (see "Personality" below). A walking statue becomes inanimate if deactivated or if the staff is broken.

Dispel Magic. You can expend 1 of the staff's charges as a bonus action to cast dispel magic on a creature, an object, or a magical effect that you touch with the tip of the staff. If the target is an unwilling creature or an object in the possession of such a creature, you must hit the creature with a melee attack using the Blackstaff before you can expend the charge to cast the spell.

Drain Magic. This property affects only creatures that use spell slots. When you hit such a creature with a melee attack using the Blackstaff, you can expend 1 of the staff's charges as a bonus action, causing the target to expend one spell slot of the highest spell level it can cast without casting a spell. If the target has already expended all its spell slots, nothing happens. Spell slots that are expended in this fashion are regained when the target finishes a long rest, as normal.

Master of Enchantment. When you cast an enchantment spell of 1st level or higher while holding the staff, you can make an Intelligence (Arcana) check with a DC of 10 + the level of the spell. If the check succeeds, you cast the spell without expending a spell slot.

Sentience. The Blackstaff is a sentient staff of neutral alignment, with an Intelligence of 22, a Wisdom of 15, and a Charisma of 18. It has hearing and darkvision out to a range of 120 feet, and it can communicate telepathically with any creature that is holding it.

Personality. The staff has the spirits of all previous Blackstaffs trapped within it. Its creator, Khelben Arunsun, is the dominant personality among them. Like Khelben, the staff is extremely devious and manipulative. It prefers to counsel its owner without exerting outright control. The staff's primary goal is to protect Waterdeep and its Open Lord, currently Laeral Silverhand. Its secondary goal is to help its wielder become more powerful.

In the event that the holder of the office of the Blackstaff no longer serves the staff's wishes, the staff ceases to function until it finds a worthy inheritor—someone whose loyalty to Waterdeep is beyond reproach.

Spirit Trap. When the Blackstaff dies, the spirit of that individual becomes trapped in the staff along with the spirits of the previous Blackstaffs. (A Blackstaff whose spirit is trapped in the staff can't be raised from the dead.)

Destroying the staff would release the spirits trapped inside it, but in that event, Khelben's spirit can lodge itself inside any one piece of the staff that remains. The piece containing Khelben's spirit has the staff's Sentience property but none of its other properties. As long as this piece of the staff exists, Khelben's spirit can make the staff whole again whenever he wishes. When the staff is remade, the spirits of the previous Blackstaffs become trapped inside it again.