|“||Your soul is very special Asriel. Mind if I take it? Akumu is hungry.||„|
|~ Bete Noire to Asriel about his soul|
Rainbow Soul is the only Monster Soul that is not an upside down heart.
The rainbow soul is a soul with a white outline, the part of the white outline changes colors. These colors are red, orange, yellow, green, dark blue, light blue, and purple.
- The Rainbow Soul makes Asriel just as powerful as a human wizard.
- Asriel is the only one who holds a Rainbow Soul.
- Rainbow Soul is just 1 soul, the soul has a small portion of each trait. It's confirmed by Camila.
- Chara's remaining soul has become a container for each trait in Asriel's Rainbow Soul.
- The Rainbow Soul is the closest a monster can get to having a determination soul.
- The Rainbow Soul is weaker than the Determination soul trait, but it's still powerful among other monsters. 
- ↑ The Rainbow Soul is the closest a monster can get to a determination soul. (Link)
- ↑ The Rainbow Soul is weaker than the Determination soul trait, but it's still powerful among monsters. (Link)
|Human Soul Traits||DETERMINATION ♡ Justice ♡ Patience ♡ Perseverance ♡ Bravery ♡/FEAR ♡ Kindness ♡ Integrity ♡|
|Souls||Monster Soul ♡ Human Soul ♡|
|Weakened Souls||Grey Soul ♡ Empty Soul ♡|
|Combined Souls||Rainbow Soul ♡ Two-Traited Soul ♡|