The terrible troll-bird
(Book)

Originally published: Garden City, N.Y.: Doubleday, 1976.

One summer's eve Ola, Lina, Sina, and Trina leave their village to gather firewood in the forest, when they're surprised by the hideous call of the terrible troll-bird, a giant rooster who pops up out of the treetops and swoops down to devour their beloved horse Blakken. Little does the terrible troll-bird know that in Ola, Lina, Sina, and Trina he has finally met his match: his terrible days of terrorizing are over. Before long the whole village is celebrating the monster's demise, and even the gnomes and hulder-maidens are coming out of their hiding places in the woods to participate in a great feast. All celebration is cut short, though, with the startling appearance of two monstrous moss-grown trolls even more terrible than the terrible troll-bird himself. Luckily, the children rise to the occasion once more, saving the day before they set out on a splendid new adventure. --from Amazon.