The Magmathief

''This giant metal hammer is crisscrossed with reddish-yellow veins and inscribed with runes that tell the tale of an ancient dwarven blacksmith who tried to ascend to godhood in a quest to destroy Lolth, the Spider Queen. Only those the smith deems worthy are capable of wielding her.''

Ability
While attuned to this weapon, you are proficient with it.

You are resistant to fire damage.

The weapon always sheds bright light in a 10-foot radius and dim light for a further 20 feet.

This maul has the siege property. (This weapon deals double damage to structures and objects.)

You gain a +2 bonus to attack and damage rolls made with this magic weapon. Additionally, creatures struck by this weapon take a further 2d6 fire damage.

As an action, you can slam the hammer on the ground in front of you to cast a modified version of the Wall of Fire spell. The wall must be cast in a straight line (Of any length up to 60 feet), it must originate from your square, and both sides of the wall are dangerous. The wall lasts for 1 minute, requiring no concentration, and can be dismissed as a free action on any of your turns. You can do this once each day, regaining the ability at dawn.

Sentient Weapon
The Magmathief is inhabited by the spirit of Dunmore Ashbreaker, who can speak to the attuned creature. Dunmore shares the senses of the attuned creature, but cannot otherwise interact with anything. He knows much about the world, and knows much more about wielding his weapons to their fullest potential.