Source: Tal'Dorei Campaign Setting Reborn

Wondrous item, very rare

These steel crossbow bolts were first created by the Jaggenstrike Clan during the Scattered War, and the secret to crafting them remains well guarded by the Houses of Kraghammer. Cataclysm bolts are usually kept in sets of ten, though anyone who holds even one can feel it thrumming with magical power. When you hit with an attack using a cataclysm bolt, the attack deals normal damage. Then roll a d6 on the following table to determine its additional effect.

d6 Effect
1-2 The bolt explodes in a blast of fire, dealing 3d8 fire damage to the target and each creature within 5 feet of it.
3-4 The bolt freezes the air around the target into jagged ice. The target and each creature within 5 feet of it must succeed on a DC 17 Dexterity saving throw or take 1d10 cold damage and be restrained until the end of your next turn.
5 The bolt releases a pulse of necrotic energy. The target takes 2d6 necrotic damage and must succeed on a DC 16 Strength saving throw or be stunned until the end of your next turn.
6 The bolt shatters to unleash a burst of shrapnel. Make six additional ranged attacks against the target, each of which has a +7 attack bonus and deals 1d6 piercing damage on a hit.

Once the bolt hits, the enchantment ends and it becomes a normal piece of ammunition.