A sinister book that forces the reader to relive painful memories by presenting idealized versions of their outcomes.
A Magic ring, made from the storm shards. It can transform the morality of a person and contain them until the world has forgotten them. In effect it renews a person after their own personal storm.
With the application of kinetic energy, this shard radiates the aura of worry, fear, and doubt that the fiercest storms bring.
Magical gem that scrys storms, and allows the wielder to “walk” them.
With a huge number of sacrificial victims, another realm long ago secretly bound a Prince of the land spirits, Iorstonn by name, thus ensuring the fertility, and improving the magical defences, of their realm. But binding that Prince to one spot has disrupted the weather and magical patterns (ley lines?) over half the continent. Things have become bad enough that a coalition has been formed to rectify the situation, once divinations have established the cause.
Your party is one of the teams assembled to do the rectification: find the binding object and steal it ("so that we can destroy it here in our realm, of course"...*) or destroy it over there. Presumably the Prince will be grateful to his rescuers and angry at the binders, but with a greater spirit like Iorstonn one can never be sure: such beings are "tricksy".
* Of course, the rulers of our realm might want to control Iorstonn for their own ends...