This metal scepter is made of black iron inscribed with runes, and is warm to the touch. At night, or during an eclipse, it whispers and mutters in Infernal. Any creature who listens carefully to the rod might learn something useful.

While holding this rod, you gain a +1 bonus to spell attack rolls and to the saving throw DCs of your warlock spells. It has the following additional properties.

Rod of the Pact Keeper. You can regain one warlock spell slot as an action while holding the rod. You can't use this property again until you finish a long rest.

Fiendish Origin. Celestials find the rod's presence repulsive.

Unbreakable. This rod can't be broken. Special means must be used to destroy it.

Sentience. The Black Rod of Nessus is a sentient, lawful evil item with an Intelligence of 14, a Wisdom of 10 and a Charisma of 16. It has hearing and darkvision out to a range of 120 feet.

The weapon can speak, read and understand Common and Infernal. It's voice is soft, even when angered.

Personality. The Black Rod of Nessus  whispers commands to the wielder. It quietly objects to any act of open charity.

The rod's purpose is to serve the Archduke of Nessus. It will periodically command the wielder to perform quests on behalf of the Lord of the Nine Hells, and will attempt to withold its abilities if the wielder opposes the actions of devils in the service of Asmodeus.

Notes: Bonus: Spell Attacks, Bonus: Spell Save DC, warlock, Sentient