Yarno is a planet that is home to the Deathcropolis and several members of The Order of the Twelve.
Background[]
The planet is featured in "Chapter 3". According to Avocato, Yarno used to safeguard refugees, so he and Gary decide to take Mooncake there to keep him out of the Lord Commander's hands.
However, upon arrival, they quickly discover the Order of the Twelve has been corrupted, and the planet has been turned into a hellhole where violence is common, and refugees are forced to participate in gladiatorial battles in the Deathcropolis.