A wicked enchantress.
She uses her attractive daughters to trick suitors into near-impossible tasks. They cannot win, as she’s on hand to destroy any that succeed.
LOUHI has the skill to transform herself into a griffin, the power to shut the Sun and Moon up in a cave, and the ability to send cold as a viable entity to inflict ice-binding if you are afloat.
She was only outwitted by VAINAMOINEN and ILMARINEN, who ran off with the magic SAMPO mill they had made for her. Even then she caused things to grind to a halt when the mill fell overboard in the ensuing water chase.