https://en.wikipedia.org/wiki/World\_Turtle

Chelonia refrence?

the tortoise from Guarma? you can skin it and draw it. 

Its not in the compendium.

this is the Mufree Brood cave near Butchers Creek.

A "giant turtle in the sky" often refers to the World Turtle (Great A'Tuin) from Terry Pratchett's Discworld series, which carries four elephants and a flat planet through space. It is also linked to Maturin in Stephen King's IT, or popular culture references in games like Fortnite and Blox Fruits

Mythology and Cosmology: The World Turtle is a common mythic figure, often depicted as a giant turtle or tortoise that carries the world on its back.

Literature (Discworld): In Terry Pratchett's series, Great A'Tuin is a colossal Chelys galactica (World Turtle) that travels through space carrying four elephants (Berilia, Tubul, Great T'phon, and Jerakeen), which in turn hold the flat Discworld.

Gaming:

Ark: Genesis DLC: Features a massive, tameable "Space Whale" or Tortoise that functions as a submersible, mobile base.

Blox Fruits: The "Floating Turtle" is a major, highly populated island in the Third Sea.

Sky: Children of the Light: A "Sanctuary Turtle" is located in the Sanctuary Islands.

Sky/Nature Interpretation: Some interpretations, including the Keya (Turtle) Constellation, connect the turtle to the cosmos, using the Big Dipper to locate it.

Other Media: Maturin is a space-faring turtle in Stephen King's IT and The Dark Tower series. 

Found a giant tortoise? Turtle? in the sky.. like that