This is hex is used by many Frost Wurms in Eye of the North.
Inspired Hex and Revealed Hex are good spells to use to remove the hex, since these spells cannot copy monster-related hexes. Pain Inverter also works well since it will kill the wurm relatively quickly if the wurm manages to cast the hex on your entire party, although interrupts are a more recommended option to deal with the hex.
Anomaly! The description does not mention that Wurm Bile inflicts a random condition when it ends.