1: Melt

Determination doesn't go well with skeletons.

You see, skeletons can't really die. They're already dead.

So how can determination revive something that's dead?

There are other reasons not to inject determination into a skeleton.

Skeletons don't have immune systems, so their magic stays in constant vigilance and tries to fight off diseases or anything foreign to their body.

Their magic doesn't do very well.

When determination goes into the body of the host skeleton, the magic tries to destroy the determination cells.

And the determination fights back.

Determination's way of fighting magic is to wriggle itself into a magic cell and take over the nucleus of the cell, controlling it.

And skeletons don't have brains, so the skeleton runs on magic to think and act.

Thus, the skeleton practically becomes determination.

Then the determination sees everything as a threat. The main threat to them is monsterkind.

Then determination cells leak out and multiply (outside of the body, of course, because they know they could kill the host by melting them) and try to make their way into another monster's body.

Then the melting starts. The skeleton melts into a big leaking version of itself. And if the magic cells hadn't been controlled by the determination, the skeleton still wouldn't be able to think.

Then the process starts again in another monster. The determination sees the brain of the monster as a threat and takes it over. Then it becomes an outbreak. Melted monsters everywhere. And nobody knows a cure... Then monsterkind all melts together into a giant made out of determination-infused monsters...

If only Dr. Alphys and Sans had known that.

Sans bursted into the lab, holding an injured Papyrus in his hands. Papyrus had a deep crack in his skull and his eyesockets were closed. "alphys, no time to explain, but papyrus is dying! do something! remember how you're going to revive those monsters? do that to papyrus! please, he's going to die!" Sans yelled.

Alphys responded, "But i-it's not ready yet! The serum hasn't been fi-"

"i don't care! just help papyrus!" Tears were welling in Sans' eyes. It looked like Sans would frown for the first time in years until Alphys brought Papyrus into the lab. Alphys gathered the determination samples and said quietly to herself, "Please work, please work, pleease work..."

She pushed the plunger on the syringe and gave Papyrus the determination.

Unexpectedly, Papyrus opened his eyes.

"Brother, I'm alive! I feel strange, though," Papyrus exclaimed.

Sans was estatic. He brought Papyrus home and they ate Papyrus' favorite treat, dinosaur egg oatmeal, and went to bed. Little did Sans know that Papyrus was being controlled by determination all throughout his sleep...