Board Thread:General Discussion/@comment-30664268-20170420225552/@comment-30664268-20170422012207

Mabian wrote:

As a second point, if Asriel did indeed absorb Chara's soul, then there would be an expected result from that theory: Chara's soul should be in some way observable. In particular, when Asriel releases the power of the souls he has collected, we see six hearts with colors (representing the six human souls that were captured), and a bunch of white hearts (representing all of the monsters that were captured), but no red heart for Chara (or any other color that could represent a seventh human soul). He lost it after death, so...maybe, a red SOUL, for Determination (Most likely), is enough to turn you into what you'd become by absorbing 7.

Hey! Here's something, that's not canon, but still:

Dremurr Reborn.

In it, once Asriel, gets Frisk's, SOUL, he becomes his kid form.

A simple normal SOUL (Kindness, Bravery, Patince), can't do this.

So, Asriel'd (If this AU's treated as canon) would only need a red SOUL.