What is an Imoogi, the villain in K-drama Tale of Nine Tailed (2020)?

Are you watching Tale of the Nine Tailed (2020) right now? Tale of the Nine Tailed (2020) The drama focuses on 100-year-old gumiho (nine-tailed fox) named Lee Yeon (Lee Dong-wook) who abdicated his position as the mountain spirit of Baekdudaegan for the reincarnation of his first love Ah-eum (Jo Bo-ah). She was killed