Serum
In Undertale Yellow, a serum is an important plot element mentioned multiple times. Not all serums mentioned in-game had their origins or effect explained in depth, creating confusion.
Chujin's Serum[edit | edit source]
After Chujin Ketsukane got fired from his engineering position in the Steamworks, he spent several years devising a plan for monsters to defeat humans in a war that he expected would break out after the monsters manage to break the barrier.[1] His plan was based on turning regular monsters into Boss Monsters, which, he assumed, would make monsterkind a way more powerful threat to humankind. It involved a serum extracted from a fusion between a Boss Monster SOUL and a human SOUL.[2] His experiments were stopped by his death, and he asked his wife, Ceroba Ketsukane, to continue his research.[3]
During Chujin's experiments, a human with the blue SOUL (Integrity) fell into the Underground and attacked a monster that Chujin's daughter, Kanako, was with.[4] Chujin sent his creation, Axis, after the human, and Axis chased the human and killed them.[5] This allowed Chujin to retrieve a human SOUL to experiment with.
During Ceroba's experiments, she tried to remove corruption from an extract of the human's SOUL.[6] As instructed by Chujin, she tried not to use Kanako's SOUL during her experiments, but when Kanako saw Chujin's tapes she insisted that Ceroba tests the extract on her. The test went awry when Kanako's SOUL received a visible crack after the injection, and she is later stated to have fallen down. Therefore, Chujin's Boss Monster serum never got created.
Martlet's Serum[edit | edit source]
During the Neutral and Genocide Route, Martlet is stated to have carried a syringe with herself in case Clover starts a rampage.[7] Martlet throws the syringe away at the end of a Neutral Route, and injects herself with it at the end of a Genocide Route, turning into her final form. The syringe is also stated to contain a serum.[8]
Not much more is directly stated about this serum. However, several assumptions can be drawn from hints given throughout the game, none of which are confirmed:
- The serum contains determination.
- Martlet is shown to enter the True Lab right after the cutscene where Chujin expresses concern for her joining the Royal Guard and warns her that humans are dangerous and cannot be trusted. True Lab had determination experiments going on around the time Alphys has been around, so Martlet could have picked up a syringe related to these experiments.
- During the second phase of her fight, Martlet melts similarly to Undyne. Martlet is stated to have fallen down at that point,[9] and Undyne's health had already dropped to 0 before she starts melting.
- The serum contains an extract from the blue SOUL.
- A drop of liquid is visible falling down from Martlet's arm after she injects herself with the serum, and the puddle it forms shortly after falling is blue in color.
- Martlet, as well as her battle interface, are themed blue during her battle.
- Whether the extract was Chujin's, or extracted from the blue SOUL after it was handed to Asgore, is unknown.
References[edit | edit source]
- ↑ They believe once he gets seven SOULs and breaks the barrier...
...he'll easily be able to overthrow whatever awaits on the Surface.
A rather foolish outlook if you ask me.
Who knows how the humans have prepared for retaliation since then? - Ceroba in Steamworks commons on a Pacifist Route - ↑ As a nation, an army, we could finally possess enough power to take the Surface back!
My theory for this involves the fusion of a human SOUL and a Boss Monster SOUL.
From that, a serum would be extracted which could transform any average monster. - Chujin in his fourth tape found in the Ketsukane Mansion - ↑ My SOUL has deteriorated and I don't know how much longer I have.
However... I believe my theory holds stronger than it ever did.
This is a message to my dear Ceroba:
This research is up to you. No one else would listen. - Chujin in his fifth tape found in the Ketsukane Mansion - ↑ A few panicked townsfolk ran up to me saying that a human had entered the area.
This human... they attacked the monster Kanako was with. - Chujin in his second tape found in the Ketsukane Mansion - ↑ The human who almost hurt my child, I told Axis to track them down. [...] Axis soon contained the subject and... hid the evidence. [...] I now have a human SOUL in my possession. - Chujin in his secret videotape
- ↑ Kanako: "Using the leftover ex... extract from the human's SOUL...
I believe I have removed any corruption it held."
Ceroba: ...Negating the need for someone pure of heart. Yes. - Ceroba and Kanako during a Pacifist Route final battle cutscene - ↑ I had this backup plan in case you started a rampage but...
...you never did. - Martlet at the end of a Neutral Route - ↑ W-What's going on?
The s-serum, it...
N-No! I can handle it! - Martlet during the second phase of her final battle on the Genocide Route - ↑ Fallen down. - Martlet's Check text during the second phase of her fight