Frost Wyrm
From Warhammer - The Old World - Lexicanum

Frost Wyrm with Katarin[1]
Frost Wyrm are powerful creatures of Ice Magic in Kislev. [1]
Swift and sinuous creatures of magic, Frost Wyrms primarily roost in the Crags of Shargun and sleep away the warmest parts of the year in hibernation, only venturing out onto the oblast to hunt prey during the coldest weather. They prey on any wandering herbivores, although in times of famine they may consume Chaos beasts too, chomping down a Minotaur or Troll with savage delight. [1]
Ice Witches
They are naturally aligned to the Ice Witches of the Ice Court who may travel to the lairs in times of coldest winter and beseech them for aid. The Ice Queen, Katarin has such power that winter itself travels where she does and no Frost Wyrm would ever refuse her. [1]