Blizz Rods are mob drops added by Thermal Foundation. They are sometimes dropped when a Blizz is killed. Essentially, they are the Blizz equivalent of Blaze Rods.
Blizz Rods only have a single use: they can be crafted or pulverized into Blizz Powder. This material is a critical ingredient for creating Cryotheum Dust and, ultimately, Gelid Cryotheum.