The vilkacis is a werewolf in Latvian and Lithuanian mythology.
Vilkacis litterally means "wolf's eyes" 'werewolf'. Alternative names include Vilkatas, Vilkatis.
The vilkacis is a human that shapeshifts into a werewolf, however it is not clear wether there is a physical transformation or the soul enter the body of a wolf. Some tales mention an apparently asleep person who appeared at miles "running like werewolf", after what the person turns out to be dead, as the soul couldn't enter the flesh to return.
On occasion the vilkacis would bring treasures - but this part of job is usually done by vilce or pūķis - or be beneficial.
Becoming a vilkacis
They say, that you can turn into vilkacis yourself without someone of them biting you - all you have to do is wait for full moon, and go under a tree, thats' top has been grown into earth, forming an arc. Then you transform into Vilkacis, although is not clear, how you get back to your original human form after that...
In the Latvian teikas and fairytales is sometimes told, that you can turn into vilkacis, if you have a wolfs' fur - you simply put it on and then say some words, and - voila! - you are a vilkacis. But in the times of witch burning women could simply be accused of witchcraft, if the fur was found in house.
Powers
Vilkacis does not seem to have powers to regenerate like its relatives in nowadays literature. It can't recover from injuries, especially mortal ones. There is a "teika" ( means "tale" or "myth" in Latvian ), that once a man left as vilkacis to hunt for barons cows, but returned soon after injured and finally died - the baron had shot the wolf that attacked his herd.
Mythology
In the Latvian mythology, particulary women would be the ones, who turn into vilkacis (they are called vilkatas, a female "version"). They have to strip completely and then leave their clothes in a place, where noone would find them, for, if someone touches them, vilkacis can't turn back into human for some time ( particulary the time is considered to be 1 to 9 years ), and in this case they would run around the house, especially, if they had a child, and houl and sometimes come closer to their husbands and children.
In later times, there were also references to German inwaders - barons and counts - as vilkacis. They were said to turn to creatures more like the "traditional" werewolves and hunt in packs consisting of their family members, particulary male ( the women of their families would always be witches in teikas ). Though this, only a few of them were agressive towards their servants, while others even offered the ones, who they met on the road, to teach, how to become one of them or sometimes even protected them from the other pack members, as showing, how kind the masters really are.
In this time, there are also legends of servants turning into vilkacis, and these creatures are very agressive, they are to hunt on the cows and sheep, but never on humans. Latvian werevolf is not like its "brother" in Hollywood films who attacks humans, tears them apart and eats their flesh. They would only attack animals, but only on condition that the cow or sheep belongs to the baron.
Evil or not?
It is also known, that Latvian vilkacis is no evil being. They are even called "Dieva suņi" ( "Gods' dogs" ), although it is not clear, which god is meant - the Latvian divinity Dieviņš, who was there before the Crusaders came with their faith, or The God.