My name is Tytti, the maid of Death, and it is my duty to inform you that you have come far enough, unless you are dead.

Tuonela, aka Manala, is the Underworld of Kalevala and River Tuoni is its River Styx. At the time of their death, people come to the shore of the river, to wait for my boat to come and take them to Tuonela. Some Shamans, eg. Väinämöinen, trick us guards of the Underworld to get in... Another way in is to use the Whirl in the middle of the world, but that isn't as easy going as the the River Tuoni.

Väinämöinen, Väinö, entered Tuonela to seek the knowledge of the Dead*; I took him over the river on the ferry boat, but his mission failed and he barely escaped, cursing anyone who'd try to do the same.

Lemminkäinen (the Loving One), Kaukomieli (Farmind), aka Kauko (cow-co) was another hero, who returned from the land of the dead. He was a redhead, probably because of eating a lot of fish and he owned a great sword, with which he boasted to make his family great. He stole a wife, Kyllikki, who didn't want to be spouse for a warrior, so they made a vow, that Kauko would not go to war, and Kyllikki would not go to whoring. She did leave, so Kauko left also, to propose to the daughter of Louhi (low-he), the Mistress of North.

Louhi agreed to the marriage, as long as he would hunt and capture the Moose of Hiisi**), bridle the gelding of Hiisi and kill the Swan of Tuonela. He finished the first two tasks and went on to do the third one. The legend says that whoever tries to shoot that bird, will be perished. A jealous Northener named "Wet Hat" shot Kauko, and he fell to the River, from which the my brother, Son of Death, picked him up and dissected Kauko into 8 pieces.
Kauko's mother searched for him up and down Kalevala, and upon learning of his death, she asked the Black Smith Ilmari to make a special rake, so she could collect the pieces from the river of Tuoni. She got all the pieces together, but despite of her spells, she failed to recover her son (see main image). As a last resort, she asked a bee to go and fetch honey from the halls of Ukko, the God of Thunder, and with a lotion made of the honey, she brought Kauko back to life.

Sources:

Kalevala translation from: Project Gutenberg
The Kalevala by Elias Lönnrot, Translated by John Martin Crawford [1888]
Kalevala – The Finnish National Epic (@ Virtual Finland)
Pronunciation guide to Finnish names in Kalevala

Main image: Akseli Gallen-Kallela, Lemminkäinen's mother [at the River Tuoni] (1897)
Other images:
Tytti image by Ahti Karjalainen
"Kullervon sotaanlähtö"-painting by Akseli Gallen-Kallela

*Tuoni means literally Death.
**) Hiisi is an evil spirit of nature

Builder: Ahti Karjalainen