The Eight Trigrams Prison is a jail located somewhere in the Heavenly Realm. The jail is said to have lava like heat.
The Jail resembles a coffin with many chains holding it. It has openings on both it's sides and front, it resides over a large fire which heats the coffin to lava like temperatures
While not used offensively this weapon is extremely hard to break out of.
Jail: The jail is incredibly hard to break out of. It was so hard to break out of that even The Monkey King couldn't break out of it without the help of his entire army
Heat: Inside the jail there is immense heat even stated to be lava like which is estimated to be 700 to 1200 degrees Celsius.
- This prison was also used to punish the Monkey King during his rebellious phase in the Journey to the West.
- In Journey to the West, this prison was meant to put Sun Wu Kong, the monkey king to death but instead the furnace gave him a steel-hard body and fiery golden eyes that can see very far and see through any disguise. This concept is seen in the God of High School as when he escaped from the furnace he was stronger and more durable than before.