What is the significance of the geas placed on Breanna by the Druid Seeress Beatha?

A geas is a compulsion laid upon a Gael’s anam (aka spirit or soul) cast by a Druid. Beatha cast one on Breanna at her mother’s request, which is to destroy the Norvegr (old Norse for a Norseman) Jarl, Hakon Skadi (aka the Dreadlord). It leaves Breanna no choice except to take a path that leads to her father’s doom.