Talk:Eight Humans/@comment-33134021-20170918202121/@comment-28517148-20170919063322

Case is bit more complicated. I think they just know it, mainly because they just understand it or because sake of story :p Chronologically the first instance that mention about it are ancient glyphs - ''Seven of their greatest magicians sealed us underground with a magic spell... There is only one way to reverse this spell. If a huge power, equivalent to seven human SOULs, attacks the barrier... It will be destroyed''. Is shows that this knowledge is quite old. However, it says about the power, equivalent to seven human SOULs, not the Souls themselves. Later, Alphys tries to get that power during her experiments from source considered as most powerfull - human Souls: ''Humans are unbelievably strong. It would take the SOUL of nearly every monster... Just to equal the power of a single human SOUL - glyphs, This is it... I will create the power to free us all. I will unleash the power of the SOUL'' - entry #1 and any other entries. Later that power is called Determination. Conclusion: the knowledge you are asking about comes from monster's old worldly wisdom about magic/souls and their experiences during war - reason why it started and how it ended.