Spirit of an old sea snake. It strangles people and eats their flesh. It hides in the darkness of the sea and waits for prey, sometimes for years.
A Wolfling is an archaic term for a wolf cub.
The Japanese name for the creature, "Hakujōshi" (白娘子) means "White Maiden" and is a reference to the eponymous character of the Chinese tale of "The Legend of the White Snake", also known as "Madame White Snake".
A white snake spirit becomes indebted to a human after consuming pills that grant immortality that he drops. She attains human form and the pair fall in love and marry, the human ignorant of her true nature.
However, a rival spirit, angry at the white snake for gaining immortailty, persuades the husband to give his wife a specific wine. She drinks it, revealing her true form, which causes her husband to die of shock. She journeys to find a mystical herb to revive him, and succeeds. Unfortunately he is kidnapped and imprisoned in a temple. In a bid to rescue him, she calls forth a flood and inadvertently drowns innocent people.
Her husband escapes, but she is captured and imprisoned. She is freed when he defeats the rival spirit.
Other variations of the tale say that, infact, the snake spirit is a demon wishing to steal the soul of the human, and the rival spirit assumes the form of a monk to protect him.