A reference sheet for Asriel (and Flowey) from my Undertale AU, HopeTale!
ASRIEL HP: 1000 ATK: 5 DEF: 10 MAG: 25
FLOWEY HP: 720 ATK: 20 DEF: 5 MAG: 150
I figured I might as well include Flowey with Asriel's ref sheet. I only showed Asriel's SOUL because Flowey doesn't actually have one.
Asriel was the son of Toriel and Asgore, making him the prince of the underground. He saw himself as more of a knight however, so when a human fell and was adopted by his parents, he was determined to be the protective brother. However, Chara ended up protecting him more. They made him a bit less overconfident though - he realised he wasn't as strong as he thought, and that that's OK. He's one year younger than Chara - 5 years old when they fell and 7 years old when the two of them died.
When Asriel died, because his SOUL was, at the time, merged with a human's, it didn't exactly fade away. Instead it dissolved, spreading itself around parts of the underground - most of it staying with the human SOUL he absorbed, which in turn dissolved into the soil where it disappeared until awakened.