The Witcher: Nightmare of the Wolf Description:

The world of The Witcher expands in this anime origin story: Before Geralt, there was his mentor Vesemir a swashbuckling young witcher who escaped a life of poverty to slay monsters for coin. But when a strange new monster begins terrorizing a politically-fraught kingdom, Vesemir finds himself on a frightening adventure that forces him to confront the demons of his past.