A few things that seem to bug me about humans and monsters in undertale and I have a little theory. Well, I have many I think of when I start playing remixes of the game tracks but I am getting ahead of myself.

What if:

The Wizards that sealed away wanted to keep monsters from being weaponized. IE hybrids that can naturally use magic and being human would have a characteristic to handle a large supply of DETERMINATION than their non-monster counterparts.

But Why would the wizards not just kill off the monsters?

I have a few scenarios about this:

  1.  Wizards were wise people and had strong heart and soul for them to use magic themselves… Maybe they were already hybrids themselves and sided with humans to save monsters.
  2. Wizards wanted to make sure all monsters were trapped and maybe in the effort to kill them all they could get away. The Spell made it impossible to get out so going to kill them would be a suicide mission.
  3. They already going to win, as humans killed monsters… they started to becoming dust-lust to become stronger by slaying these beasts. If some weaker ones were captured and used as breed stock they could use them as means to get stronger and lose more of their humanity.

Ok, but would species be unable to breed?

Normally I would agree with you on that front because it would be a matter of biology and it is unlikely with the knowledge we have at our fingertips. However, we are talking about magic and monsters looked different from each other. MAGIC would be the counter to this problem, it could make hybridization easy and maybe make some badass looking creatures. So the process could be done by a ritual as well.

Honestly, How strong are we talking here? There would be a drawback…

Yes, at first “They” might be weaker or not even possible. If a ritual unless its natural mutual affection for both parties. Maybe this could also be an unbalanced creature that could be a feral beast.

Maybe the Wizards were considering methods to stop and bring peace to both factions. However, there have to be some monsters still lurking around outside the barrier that humans have missed or can’t find. The outright hatred still bought concern.

however, if a hybrid was very powerful and easy to get stronger by sheer DETERMINATION it could be possible to overrun humans and monster into relics of the past. Making it a Threat but this would be a problem for normal monsters as well as humans if this worst case was played. So it’s possible the Wizards make a choice to seal them so maybe in the future they got free peace and balance would be ensured or humans would be too advanced to consider cross-breeding as an option or humans would have wiped each other off the world and monsters would have rebuilt the world as a fail-safe.

But that’s just a Theory, A Undertale theory.

Thanks for Reading, If you have any input on this theory or want to share your own fill free to like a comment in the box below!

P.S.: Here some remixes I been listening to and if you like them go to youtube and give the original remixer some love.