Deok-Hwa is not a deity, but a human being temporarily possessed by the Supreme God. We don’t know exactly what the Supreme God’s name is right now.
While Kim Shin was dying in the field during the Goryeo era, we can hear Goryeo people desperately praying to the sky “Please, Dear Chil-seong-nim (칠성님 七星), Dear Cheon-Ji-Shin-Myeong-nim (천지신명 天地神明)” etc.
Chil-seong-shin (칠성신 七星神 meaning “Seven star gods”) is originated from the constellation of the Big Dipper in the sky. They are seven Gods in charge of life and death of Human beings in Korean folk religion.
Cheon-Ji-Shin-Myeong (천지신명 天地神明 meaning “The god of heaven and earth”) is the Supreme God. If you are a Sageuk drama fan, you can often see people praying to him, rubbing their both hands to the sky. Most English subtitles used to translate him just “Heaven” or “Heaven God” as far as I know.
The image of Chil-seong-shin and Cheon-Ji-Shin-Myeong has been mixed for a long time. So, it is safe to say that both of them refers to the same Supreme God in Korean folk religion. He has a similar function or position to Jeho Vah / Yahweh (Christianity), Indra (Hinduism), Zeus (Greek Myth), Jupiter (Roman myth), Odin (Nordic myth), and Jade Emperor (Chinese Taoism) etc.
Therefore, according to Korean mythology,
You are created by Samshin Granny (삼신할미 三神), the Goddess of Childbirth who protects mothers and children. You are protected by her until you become 10 years old.
You live a life under the rule of Cheon-ji-shin-myeong (천지신명 天地神明, the god of heaven and earth). All human affairs are under his control.
Also, there are many deities and mythical creatures including Dokkaebi (goblin) and dragons (sea god) that interfere with human affairs.
You meet a Grim reaper when you die. They are called “Jeoseung Saja (저승사자)” in Korean which literally means “A messenger from Netherworld”
In the courtroom of Netherworld, everything you did during your life time will be judged by King Yeom-Ra (염라대왕 閻羅大王) who is Grim reapers’ boss and the lord of Netherworld.
If you are good enough, you will be sent to heaven or reincarnated into the next life.
But if you are guilty, you will be tortured in the hell for a long time. In some cases, you can be reincarnated into an animal.
If you have strong desire or deep grudge to remain in this world, you will be a spirit (ghost) roaming around the world.