Grovelthrash

From Explorer's Guide to Wildemount, pages 275-276.

Description
Weapon (warhammer), artifact (requires attunement).

Crafted from a single piece of obsidian, this warhammer of Torog hums with magical energy and is carved with the images of faces screaming in pain.

Sentience. Grovelthrash is a sentient neutral evil weapon with an Intelligence of 18, a Wisdom of 15, and a Charisma of 19. It has hearing and darkvision out to a range of 120 feet.

The weapon communicates telepathically with its wielder and can speak, read, and understand Abyssal, Common, and Infernal.

Personality. A covetous ultroloth named Ciria lives within Grovelthrash. The weapon values material possessions and doling out pain. It compliments its wielder whenever they claim treasure and takes pleasure in harming others.

Dormant. The warhammer grants the following benefits in its dormant state:
 * The warhammer has one minor beneficial property and one minor detrimental property.
 * You can speak, read, and write Abyssal and Infernal.
 * You gain a +1 bonus to attack and damage rolls made with this magic weapon. When you hit with an attack using this warhammer, you can deal an extra 2d6 bludgeoning damage to the target. If you do, you take 1d6 psychic damage. The warhammer deals double damage to objects and structures.
 * While holding this weapon, you have advantage on Wisdom (Insight) checks made to discern a lie spoken in a language you understand.

Awakened. When the warhammer reaches an awakened state, it gains the following properties:
 * The warhammer gains an additional minor beneficial property and an additional minor detrimental property.
 * The weapon's bonus to attack and damage rolls increases to +2.
 * You gain a burrowing speed equal to your walking speed. You can use your burrowing speed to move through sand, loose earth, mud, or ice, not solid rock.
 * When a creature you can see within 30 feet of you hits you with an attack while you are wielding the warhammer, you can use your reaction to deal an amount of psychic damage to that creature equal to the damage you took from the attack. This property can't be used again until the next dawn.

Exalted. When the warhammer reaches an exalted state, it gains the following properties:
 * The warhammer gains a major beneficial property.
 * The weapon's bonus to attack and damage rolls increases to +3.
 * When you have fewer hit points than half your hit point maximum, the warhammer deals an extra 2d6 bludgeoning damage on a hit.
 * You can burrow through solid rock at half your burrowing speed and leave a 5-foot-diameter tunnel in your wake.
 * As an action, you can use the warhammer to cast one of the following spells from it (save DC 17): Earthquake, Meld Into Stone, or Stone Shape. Once a spell has been cast using the warhammer, that spell can't be cast from the warhammer again until the next dawn.