Wondrous item, uncommon
When found, this leather bag is filled with 1d6 + 2 smoldering coals. They remain hot within the bag, keeping it warm to the touch on the outside. When a coal is placed in a fire, such as a campfire or forge, the fire remains at its optimal temperature (based on its original intended use) for the next 8 hours without having to add any additional fuel to it. At the end of the 8 hours or when the coal is removed from the fire, roll a d4: on a 1, the coal sputters out and ceases to be magical. A creature that finishes a short or long rest within 15 feet of such a fire gains 2d4 temporary hit points.
Alternatively, you can use an action to drag a coal across a nonmagical weapon. For the next 8 hours, that weapon deals an extra 1d4 fire damage to any target it hits. When you use the coal in this way, it then ceases to be magical.
Sharpen your soul, sharpen your steel.