Ysätters-Kajsa

According to the account preserved in Selma Lagerlöf's narrative and summarized in modern references, she was called Kajsa because 'wind-trolls used to be called by that name' and received the cognomen Ysätter from the swamp Ysätter in Asker parish where she was said to have been born. The tale frames her as a single, localized being tied to that place and to the Närke plain.

Lagerlöf's literary portrayal personifies her as a female troll integrated with the storm: she is described as standing in the centre of a whirlwind, with long hair whirling among the clouds and a skirt dragging on the ground like a dust storm, and as sometimes sitting atop a high Scots Pine on a cliff watching the plain. These poetic elements come from Lagerlöf's narrative rather than a catalogue of ethnographic descriptions.

Reported actions in the sources (chiefly Selma Lagerlöf) attribute to her control over winds, whirlwinds and localized weather phenomena: raising gales, creating whirlwinds and dust-storm-like trails, bringing fog that misleads travelers, causing sudden rains or snowdrifts that affect farming and transport, puffing on charcoal kilns so fires burn brightly, blowing laundry and tableware about, displacing hats and disturbing smoke into houses, and nudging small boats onto shoals. She is portrayed as mischievous rather than wholly malevolent and is said to be morally selective—harassing quarrelsome or mean people while sometimes protecting honest folk and children (including a story in which she extinguishes a church fire).