Mestaritontun seikkailut

This is one of the first “fantasy” I ever read. It is actually a fairy tale, about the “mestaritonttu” - master gnome? Though the Finnish tonttu are not really gnomes... or maybe they are, I don't quite know what gnomes are. Tonttus are elf-folks, small, they look like very old people, and they have magic. Anyway, I need to reread this, because I have forgotten the most important parts of this :-D
I just remember there were witches - not like people with magic, but being their own magical species, like fairies, gnomes, mermaids - all of those are in this story. There's a lot of Finnish mythological species. Mestaritonttu worked for a fairy king whose daughter married the sea king's son... she might have been abducted, a little bit like Persephone and Hades... anyway, there was a pearl that shone a light, and this was stolen or something, by the witches, and Mestaritonttu fetched it back... might be that he also managed to rescue a prince, who then fell in love with another princess, or something... :-D Yeah, I read it about 30 years ago, maybe even more than that :-D
But it was really good.

Reread 2021 :-D
I remembered it quite well, though not well enough.
The tonttu worked for the king of Fairytale Land, whose daughter married the Sea King's son, and hadn't visited her parents ever since. The father misses her daughter dearly, so when the tonttu sees the daughter at the sea and fails to call her in, the father gets angry with his most loyal servant, and the tonttu gets so upset he leaves the Fairytale Land.
He gets picked up by a witch, Sammaleinen, who is apparently quite a tall and manly figure, not like the one on the cover, because later in the book the prince of Fairytale Land impersonates her and no one notices any difference.
Anyway, the witch wants some company and Mestaritonttu agrees to become that to her. He doesn't want to live in her witch cottage which is a rather dark and moldy and stinky place, but goes and finds himself another place to live in. This is on top of a big rock, and at the night he dreams that there is a princess hidden inside the rock. That dream turns out to be true, and after several adventures, he manages to save the princess with his friends, and this princess' brother saves the daughter of the Fairytale Land from the Sea. (Her husband has died, but the Sea King doesn't allow her to go back home.). The book ends with a double wedding, the son of the Fairytale Land's king marries the princess of Dawn (who was locked in the stone), and the daughter of the Fairytale Land's king marries the King of Dawn, the princess' brother.
It is a very thrilling story, with rather clever twists and solutions, and a lot of Finnish mythological creatures. I still love it. :-D
One day I will either translate it, or rewrite it.