In Finnish folklore, Väki is the life force that flows in every single living creature and being. It is similar to the concept of mana in Hinduism, life force chi in Chinese culture or the Force in Star Wars. Väki literally means a group. It describes the power/group or spirits that reside in a certain idea/concept/element or being.
Väki of the elements
When a person was a practitioner of witchcraft (in Finnish context) what they essentially were doing was work with väki. Everything has its own väki; nature, trees, animals and all the elements. The idea of elements is very common in Finnish myths and all the elements possessed their own väki. Ilmanväki (väki of the air), tulenväki (väki of the fire), maanväki (väki of the earth) and vedenväki (väki of the water). From the elements, väki of the water was considered to be the most powerful because of the healing powers of water but also because the water was seen as something eternal. The woman grew children in the waters of their womb. The earth was born from waters and water always returned in some form, was it then rain or snow.
Väki of the animals
Väki of the animals was always connected to their element. For example, väki of the bear was connected to the earth and the power of the forest. Birds possessed väki of the air. Fish and frogs were part of the väki of the water. In spellcraft, if a person wanted to perform a ritual that needed elements from certain väki they used animal parts from an animal that belonged to that väki.
Some animals possess extremely strong väki. One of those animals was a wild deer. If a person ate the brains of a wild deer they would sleep very restlessly and see nightmares of dark figures, which were shadow beings of the forest.
Even the smallest animals like ants and spiders possess their own väki. Väki was always connected to the myths and stories told about the animals.
Väki of women
People also had their own väki. Woman´s väki was considered the strongest because women were the creators of life. Women had an important role in ancient Finno-Baltic societies. If a man wanted to marry a woman they had to ask permission from the mother of the bride and when the father of the household died the oldest son did not inherit the house-stead but the widow did. Väki of the women was also feared by the men occasionally. If the man cheated the woman the woman could raise their väki and hurt the man as revenge. A woman´s status was connected to her marriage and later on her becoming a mother and a grandmother. This idea is directly based on the mother earth cult and ancestral worship where the passed away grandmother became a worshipped figure.