Wylfen Fang Blade

The Wylfen Fang Blade is a shortsword that can be energized with the essence of a wolf. The wielder can increase the damage output of the weapon for fifteen minutes by drawing on a pool of magic built into the sword. Once the magical pool is depleted, the sword becomes a common shortsword. While charged in this way the blade gives off a light icy-blue glow.
Originally the weapon belonged to The Wolf and was part of his set with the Wylfen Keeper Blade.
Notes: Can only activate 1-3 charges at once for an extra d6 for each charge used. Once all charges are expended, this sword becomes a common shortsword. , Must be attuned to in order to use the magical abilities of the weapon., Finesse, Light

Mechanics & Inner Workings

As a free action at any point during their turn, the wielder can add 1-3 charges to the weapon to increase the damage dealt to creatures for the duration of the charge. Each charge is an additional d6 of piercing damage. The charge lasts 15 minutes.
Once the 15 charges are depleted the weapon reverts to a common shortsword.

https://www.dndbeyond.com/magic-items/2957249-wylfen-fang-blade

Item type

Weapon, Melee