Graz'tchar

 is a sentient greatsword that Graz'zt, the Demon Prince of Indulgence, left behind when Zan Tal'Dorei's forces defeated his army and banished him back to the Abyss.

Appearance
Graz'tchar appears to be a noble and kingly: a beautiful, cruciform, silver greatsword inlaid with rubies. It appears to do extra radiant damage to humanoids when activated. A creature with truesight can see its true nature: rusted, pitted, and dripping with acid.

Personality
Graz'zt speaks through Graz'tchar, so its personality is his. Specifically, Graz'tchar pretends to be a wise and sorrowful lost Sovereign of Tal'Dorei, beckoning the wielder to seize their destiny. The sword also attempts to slowly sway the wielder toward sowing chaos in the realm by telling lies about great leaders and claiming that the heads of the Tal'Dorei Council are corrupt and must be overthrown.

Potential wielders of the weapon may have dreams in which they have visions of the sword surrounded by shadows and demons, and hear it whispering, "Free me... I need your help... I am in the Grey Valley."

Background
In the final battle of the Scattered War, Zan Tal'Dorei's forces backed King Trist Drassig's army into a valley at the base of the Cliffkeep Mountains, but Drassig pledged his service to Graz'zt in exchange for the power to smite his foes, and so during the Battle of the Umbra Hills a flood of fiends, including Graz'zt himself, poured into the battlefield in support of Drassig. Against all odds, Zan Tal'Dorei's forces prevailed and banished Graz'zt back to his Abyssal prison. Graz'zt left his sword behind, and in the accursed Grey Valley where it lay, twin hezrou demons guard it, pretending to be the ghosts of great knights protecting the great blade of a lost Sovereign of Tal'Dorei.

Features

 * The wielder gains a +3 bonus to attack and damage rolls with this magic weapon.
 * Corrosive Submission: When Graz'tchar hits a humanoid, the wielder may cause the target to take an additional 3d6 damage (see notes on damage type in Secret Features below) and make a Charisma saving throw (DC 14). On a failure, the target is charmed by the wielder for up to one hour. If the wielder hits the humanoid again while it is charmed, the additional damage increases to 10d6, the charm ends, and the target cannot be charmed again in this way for 24 hours.
 * Sentience: Graz'tchar has an Intelligence of 14, a Wisdom of 12, and a Charisma of 18. It has hearing and darkvision out to a range of 120 feet. It can speak, read, and understand Common, and communicate telepathically with its wielder.

Secret Features

 * Hidden Nature: The additional damage dealt by this weapon is acid damage but appears to be radiant damage, and a creature charmed by this weapon is under the illusion that the damage was just an admonishing jostle. A true seeing spell or the like reveals the true appearance of the blade.
 * Personality: (See Personality section above.) If the wielder disobeys the urges of Graz'tchar for an extended time, it can attempt to charm the wielder, forcing a Charisma saving throw (DC 14). On a success, they are immune to the sword's charm for 24 hours. On a failure, the wielder is charmed by the sword for 24 hours, and it can force the wielder to make one action of its choice per hour for 24 hours, the wielder accepting this as their own will. If the chosen action leads to the harm of a non-hostile creature or ally, the charm immediately ends.