The flute has 3 charges.

While holding it, you can use an action to expend 1 charge to attempt to play the flute to ignite a creature or 5 foot square surface within 30 feet of you. Once a charge is expended, the player must make a performance check DC 10 (unless they have proficiency with flutes) or the flute ignites them instead. After a successful performance check the target surface will be ignited or, if targeting a creature, that creature must make a DEX saving throw DC 15. Creatures covered in flammable liquid  must make a DEX saving throw DC 20 instead. On a successful save the creature avoids becoming ignited. 

Ignited creatures take 2d6 fire damage at the start of their turn. The ignited creature can repeat the save at the end of its turn or use its action to fall prone and put out the fire that way.

The flute regains all charges at dawn.

Quest: Successfully playing the Will of the Wisp 3 times in a day will grant the player proficiency with flutes.

Notes: Damage, Control, Combat, Warding