"Okay, see, this is your soul."

"Uh-huh. The red one."

"And this is my soul."

"...yeah."

Before them was a chart, a sort of scale. From bottom to top there were souls of different "DT levels," the red souls at the top being the ones with the highest amount of Determination, the grey upside-down souls at the bottom being the ones with the lowest. As in none. Monsters were at the bottom, with grey-souled humans being next, and all the other six soul colors in between... until you got to Chara's red soul.

"But just because you have a red soul doesn't mean you've got the highest possible amount of DT. You're probably close to a different-colored soul, so near the bottom of the red soul scale." Asriel was explaining as he had learned it, having read an old book while they looked for more information on how souls worked with the barrier. "So you're not like, all-powerful or anything."

"If I was, I could free everybody..." Chara muttered, staring at the chart miserably. So far they hadn't really gotten anywhere with their research.

"Don't worry about it, Chara! You're just as stuck here as we are." As if that was reassuring, but they figured he meant at least they were stuck together. "Anyway, we'd need seven human souls to break through the barrier at all. Even if you had the highest amount of Determination, you wouldn't affect the barrier any more than anybody else can."

They fell backwards onto the carpet of their room, groaning. That was the opposite of reassuring! They were the human here, so they were responsible. All the other humans... they wouldn't do anything about it. They were awful.

"Let's just go build a snowman or something, I can't take this..." they sighed, rolling over onto their side... and spotting a certain other book under Asriel's bed. "...what's that one?"

The young monster peeked over at what they were looking at, suddenly looking nervous. "That? Oh, i-it's... just a book that dropped under there, I guess. Come on, let's not waste any more time on this."

They stared at it suspiciously from their position, but eased up a bit and said, "Okay. Whatever you say, Ri." They sat up as Asriel stood, the two moving to make their way to the door.

And later, when they returned home and Asriel went to the kitchen, the human went unnoticed to their room and grabbed the book immediately, having been bothered all day. Considering how he was acting, Asriel didn't want them to see this one? But it was just another book with more useless soul information...

Until...

"...monsters who absorb human souls will become...?"

...they realized what they had to do.