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For levels using the Creo song, see Nautilus (Disambiguation).

We were nothing to Jestar but tools…He replaced us…You have to stop him!
- Nautilus, Surface Tension

Nautilus is a character created by ol666. He was originally an opponent in the levels Nautilus and First Crush as an assassin working for Jestar Heart, but eventually turned to be on the player's side starting with Surface Tension.


Chapter 1

Nautilus appeared as one of Jestar Heart’s assassins in First Crush, where he tried to take the player's souls with Aura. Although the two of them failed, he later returned to attack by himself in Nautilus. After being taken over by The Core and being formed into N.A.T.U. in Party Time, possibly against his will, Nautilus wasn’t seen again until Black Heart's second chapter.

Chapter 2

In Surface Tension, Nautilus was the only assassin left alive to suffer alone after Medusa turned the rest to stone. He revealed that Medusa was created with a clone of his body, and after breaking out of the Heart Locket with the player, Nautilus decided to be an ally and help to stop Medusa.

Nautilus reappeared in the level Medusa, near the end, to save the player at the last second from a deadly attack. This was able to temporarily defeat Medusa, however, they were quickly teleported away, possibly by Jestar.


Nautilus is a blue square with a black outline. His face has two black, rectangular eyes. Nautilus has two blue square hands - each with two gray spikes that resemble claws.


  • Attacking with lasers, bullets and pulses
  • Growing in size and rolling around the screen edges
  • Rotating the entire screen
  • Slamming the ground to create shockwaves


Nautilus doesn't speak until Surface Tension, so his thoughts and personality before this are unknown. After this level, however, Nautilus is presented as being determined to save the frozen assassins and defeat Jestar alongside the player. He deeply regrets his actions as an assassin and wants to set things right.


Main article: The Core
N.A.T.U is a combination of Nautilus and The Core, created seemingly against the former’s will. It is a square covered with grey, metal plates. It also has a red, hexagonal eye.




  • Nautilus’ eyes become rounded when he uses his laser attacks.
  • N.A.T.U. has no canonical meaning, despite appearing to be an acronym.
  • He is one of 3 Black Heart characters to be named after songs, with the other two being Aura and Medusa.
  • As a joke, Nautilus was also featured as a Glock in Song of Storms as Glock-ilus. Despite this, he still appears as a boss in the "bOLss rush."



Characters Nautilus - Aura - Puffer - Siren - Solario - Colossus - The Core - Myst - Perry - Jestar Heart - Medusa - Predator
Chapter 1 First Crush.jpg Running My Head.jpg Nautilus.jpg Aura.jpg Total Destruction.jpg How deep is your love.jpg Peer Gynt.jpg Party Time.jpg Exoplanet.jpg A New Dawn.jpg
Chapter 2 Surface Tension.jpg Medusa.jpg FunkHoleBHThumb.jpg