Mug of Warming

This quilted-patterned mug is perfect for cold winter nights or when caffeinated beverages are a morning necessity. Any liquid poured into the mug is instantly warmed to a piping hot temperature, remaining hot even when poured out. The mug has no effect on any form of magical liquids poured into it. The mug has 3 charges and regains 1 charge each dawn. You can use an action to expend 1 charge, splashing the contents of the mug into a 5-foot square in a conflagration of flame. Creatures and objects in the area make a DC 10 Dexterity _saving throw_ , taking 1d4 fire damage on a failure. If you expend the last charge, roll a d20\. On a result of 5 or less, the mug loses its warming properties and becomes a mundane item.