As you cast Windrunner's Spear you invest a weapon you touch with the power of wind and truth. The weapon becomes a shimmering silver spear for the duration of this spell the shimmering spear functions as a +1 silvered spear. Until the spell ends, the weapon emits a soft silvery light in a 10-foot radius and dim light for an additional 10 feet. In addition, weapon attacks made with it deal an extra 2d8 thunder damage on a hit. If the weapon isn’t already a magic weapon, it becomes one for the duration. 

If the wielder relinquishes the spear, willingly or not, it immediately reverts to its previous state and the spell ends.

As a bonus action on your turn, you can dismiss this spell and cause the weapon to emit a burst of wind. Each creature of your choice that you can see within 30 feet of the weapon must make a Constitution saving throw. On a failed save, a creature takes 4d8 thunder damage, and it is deafened for 1 minute. On a successful save, a creature takes half as much damage and isn’t deafened. At the end of each of its turns, a deafened creature can make a Constitution saving throw, ending the effect on itself on a success.

Spell adapted from Spear of Valarian from Book of Exalted Deeds 3.5 sourcebook and current 5e Holy Weapon for balance. Flavor based on the Stormlight Archive book series by Brandon Sanderson