This article, Theta Turtle, is owned by PipMcGee. Please do not edit this article without their explicit permission.


The Theta Turtle is a turtle with the greek letter Theta (Θ) on its shell. It stands on an orange pod which either has a 2 or Delta Run on it. The Theta on it's shell changes color depending on what it is doing. When it's attacking, the theta becomes yellow, when defending, it becomes green, when falling, it's blue, when unable to move it is purple, and when it is red that means that Theta is not using magic.

Theta Turtle Updated Battle Sprite

The Theta Turtle's Battle Sprite

Theta changes appearance slightly changes when attacked enough times or attacked in the Genocide Route. When this happens, Theta's eyes glow red and several red cracks in his shell appear. Four large hands appear wielding swords. These hands are projected from the pod Theta stands on.

Theta lives in the Dark Swamp, which is only accessible if the protagonist is aware of the Dark Swamp's existence, which will make them able to ask the River Person to take them there. Not finding the Dark Swamp will not affect a Pacifist or Genocide route, but if it is explored, befriending/killing the inhabitants is necessary for those routes.

Theta is at first tries to fight the protagonist, but is much nicer once spared. However, if fought enough he becomes angry at the protagonist, hating them personally instead of attacking them for Asgore.


Theta does most of what he does for personal gain. However, when able, he will help people in need. He is torn between freeing monsters and protecting humans. He is very cautious at all times, but makes rash decisions when forced to act quickly.

When humanity sealed the Monsters underground, Theta became vengeful. Because of this, when Chara fell into the underground, Theta became very suspicious. However, after Chara and Asriel's death, Theta realized how similar the two species were. This led him to research both humans and monsters extensively, even stealing lab information from Gaster's lab in the period after Gaster's death but before Alphys was appointed Royal Scientist. As a result, he gained a large amount of knowledge on the two species

Theta has an obsession with Surface turtles, and has wondered why so many monsters resemble Surface animals, but have so many human qualities, such as the ability to intelligently communicate. He is unable to find a reason.


Theta does as Asgore requests in exchange for money. As a result, knowing that Asgore, as well as most monsters in the Underground will need Human SOULs, he tries to kill the protagonist. However, he is hesitant about doing this until he feels the protagonist is against him or a threat to him personally.

Theta has helped the Royal Guard several times, which has caused him a lot of regret. This causes his attacks to not be very powerful in the First Phase of his Neutral Route fight. However, if he feels the protagonist is dangerous to him, then he will attack the protagonist with all of his power.

Relation to other Characters


Theta's relationship with the protagonist depends on what happens during their fight. If they are spared before phase 2, they'll allow them to befriend him, as well as if phase 2 was entered, but the protagonist gained no EXP.


Theta met Sans while Sans was at his post in the Dark Swamp. Eventually, Sans started coming to the Dark Swamp less and less, until he stopped coming entirely.


Theta doesn't know Undyne very well, but has given her and previous members of the Royal Guard help with human-hunting. He feels very guilty about this.


Theta met Gerson during the war between Humans and Monsters. Later, he helped Gerson with his shop, but left having found a home in the Dark Swamp


Theta used to do work for ASGORE that the king could not do himself. Later, however, he dedicated himself to locating humans, and doing whatever necessary to get their SOUL to ASGORE.


14 Attack

50 Defence

1445 HP





"I'm surprised you found this place."

"But, since you did, I have to kill you."

"It's not personal, but it's what I have to do."

"Anyway, let's get this over with."



"How did you find this place?"

"Please, don't hurt me."

"I never did anything to you, at least, not in this universe."

"This is your chance to stop your path."


During Battle


"Yeah, I understand that." [FIGHT 1]

"Did you really have to do that?" [FIGHT 2]

"This is starting to hurt." [FIGHT 3]

"Why do I keep doing this?" [FIGHT 4]

"Is the extra money from ASGORE worth it?" [FIGHT 5]

"No, it isn't. Human, I'm sorry about what I did. I don't expect you to forgive me, but if you could at least accept my MERCY, that'd be great for everyone." [FIGHT 7]

[If Spared] "OK, that was easy"

[If Fought] "What? I offer you a chance to stop fighting, and you reject it? Well then. OK, I can play that game too."

(Phase 2 Begins)

"Sorry, I can't do that" [MERCY]

"I'm sorry, it's not personal" [MERCY 2]

... [MERCY 3 & 4]

All right, if you're that determined to stop FIGHTing, I'll accept you're MERCY" [MERCY 5/MERCY after ACTing 3 times]

[If Spared] "OK, that was easy."

[If Fought] "... What is wrong with you? You work so hard to spare me, just to FIGHT? Even I don't do that!"

"Ha..." [Joke]

"Ha Ha Ha" [Joke 2]

"(bursts into laughter)" [Joke 3]

"There is no weather down here." [Talk]

"..." [Talk 2]

"Why are you talking to me? This is a FIGHT." [Talk 3]


"..." [If the protagonist neither FIGHTs nor Spares]

"Wait really? Great! Thanks for not kill me I guess" [MERCY]

"I was hoping it wouldn't have to come to this." [FIGHT]

(Phase 2 Begins)


"So, I know you're used to fighting traditionally, with the idea of lowering you're opponents HP down to 0, but there are some people with really low HP who can move fast enough to dodge lasers, like you, which gives you an unfair advantage. So, I did some research, and decided to make some advantages of my own."

"You see these hearts? They look a lot like SOULs, as you see, and to beat me, you have to get rid of them all." [Beginning]

"Now, unlike a lot of these Monsters, I know your secret" [Turn 2]

"If you die, we all just forget it." [Turn 3]

"And you get to try again." [Turn 4]

"However, you don't erase the timeline where your dead" [Turn 5]

"Usually I'd regret even the creation of that timeline" [Turn 6]

"But I offered you MERCY, and you attacked me." [Turn 7]

"That means you're dangerous," [Turn 8]

"What, am I right? OK, because to be honestly I was just guessing." [Turn 9]

"Back to the point of this, you've shown me that you're dangerous." [Turn 10]

"That sounded really hypocritical" [Turn 11]

"..." [Turn 12]

"But at least I legitimately tried to spare you." [Turn 13]

"Anyway, you might have wondered how I was able to survive." [Turn 14]

"This pod I'm standing on is very highly advanced technology" [Turn 15]

"Not only is it able to create these giant hands you see, but it is also able to keep me alive through otherwise survivable things, like for example, reaching 0 HP." [Turn 16]

"So it's really good for moments like these." [Turn 17]

"It's also pretty useful when you've been at 1 HP for over 18 turns." [Turn 18]

"Anyway, we have a problem." [Turn 19]

"You're still alive." [Turn 20]

"I get that you're really determined, but still, It isn't easy to beat me" [Turn 21]

"If you stay alive for very much longer, I'll have no choice but to use my special attack." [Turn 22]

"It will leave you shell-shocked" [Turn 23]

"Yep, my special attack." [Turn 24]

"I don't have a special attack" [Turn 25]

"..." [Turn 26]

"I've run out of stuff to say." [Turn 27]

Flavor Text

Theta blocks the way [Encounter]

Smells like Turtles. [Neutral]

Theta regrets his actions. [Neutral]

Theta Turtle notices that only the word Theta is shown on the dialogue box without breaking the 4th wall. How? Magic. [Neutral]

Theta awaits your actions [Genocide or FIGHT 7 or MERCY 5]

Theta asks himself why he's doing this [FIGHT 2-5]

Theta doesn't look at you [MERCY 3-4]

You ask Theta how the weather is [Talk 1]

You ask Theta is doing [Talk 2]

You ask him how he's doing again [Talk 3]

You tell Theta a Turtle pun [Joke 1]

You tell another Turtle pun [Joke 2]

You tell Theta another joke [Joke 3]

A turtle with a Theta on it's back. [Check]

Phase 2:

It's personal now. [Neutral/Encounter]

Everything is clear to Theta. [Neutral]

Theta is enjoying this fight. [Neutral]

Theta is considering his hypocrisy [Turn 11]

Theta is worried [5-7 SOULs left]

Theta is scared [4-2 SOULs left]

Theta is tired [1 SOUL left]

Theta is giving you one last chance to Spare him [0 SOULs left]

A turtle with a desire for revenge [Check]


Theta starts the fight normally. However, once hit 7 times, or the spare condintions are met, and then he's hit, no matter how much damage is done to him before that, he will go down to 1 HP, and shield himself. He then creates 10 hearts resembling Monster SOULs above him. To beat Theta, all of these SOULs must be destroyed through the Yellow SOUL mode.

Throughout the battle, Theta attacks by changing the opponents SOUL mode. Their Theta is usually yellow while they're attacking, but occasionally they will turn it blue to slam into the bullet board, causing rocks to fall.

To SPARE Theta, they must either be fought 7 times, Spared 5 times, or Talked to or Joked with 7 times. If attacked while these conditions are met, he will go into his second phase.

Presence in AUs

AUs Outside of Undertale RP Wiki

Note that I own none of the following, nor do their canons in anyway include the Theta Turtle


Underswap!Theta is swapped with Webdings Orbitron. Their personalities do not at all swap.


Theta is now renamed to Koup. Rather than have a theta on his shell, he has an A.


No canon characters change the human's SOUL mode to over 2 different colors, meaning if Theta was canon, they would be the only canon character to do this.


All information is by me (PipMcGee), and the picture in the infobox is by me.

If there is a double asterisk (**) it means that a character or AU, OC, or any other information comes from someone that isn't me or Toby Fox.


Theta's themes are Alpha Theta and Power of Theta (whose title is a parody of Power of NEO.) However, the music has not been completed yet.

Theta's real name is Koup Asethy

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