Ghostfire Jack O' Lantern (5e Equipment)

Wondrous item, rare (major) (requires attunement by a spellcaster)

When you reduce a living creature to 0 hit points while you are holding this magic jack o' lantern, you can use a bonus action to absorb energy from the creature's soul, gaining 1 charge. The jack o' lantern can only hold 3 charges at any given time.
When you cast a spell at its lowest level, you can expend a number of charges equal to the level of the spell slot used. Instead of expending a spell slot, you expend charges stored in the jack o' lantern.
Once you have cast 3 levels worth of spells in this way, the jack o' lantern can't be used again until the next dawn.