This article, Theta Turtle, is still being written by its owner PipMcGee. They apologize for the inconvenience.

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 Rune 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


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.





"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."


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