Cataclysm Bolt

Catalysm Bolts are magical crossbow ammunition that have a random unpredictable additional area effect damage bonus.

Description
The bolts act as normal crossbow bolts, but on impact, the user rolls a d6 to determine the kind of additional area effect damage that may occur. Caleb described them as reacting in a variety of ways upon striking their target: exploding to shrapnel, freezing the air, or bringing death to someone. The two forms of damage that were actually rolled were fire and cold. On a roll of 1-2, the damage would have been explosive fire; on 3-4, explosive cold and an area effect of restraint.

History
The Mighty Nein found three Cataclysm Bolts inside a case in Vokodo's lair, and Veth took them. She used the first one against Gelidon in Eiselcross, but the additional damage roll was for cold, which Gelidon was immune to. The remaining two were used against the fire guardian on the Elemental Plane of Fire, and both additional damage rolls were for fire, which the guardian was immune to..

Trivia

 * The third type of damage (on a 5-6 d6 roll) which was never seen, "bringing death", was likely necrotic damage.
 * All three times Veth used the Cataclysm Bolts, the creature was immune to the extra damage from the bolts.