The Monster Realm is a plane of existence in which all Monsters originate from.
The Monster Realm is the realm where all Monsters come from. The realm is a large planet the size of the Sun located in the Milky Way Galaxy. There are multiple continents located in the Monster realm, each ruled by a different Monster.
Although most monsters decide to live peacefully in the Monster Realm, others decide to rather instead escape into the living realm through Realm Portals. The reasons for why they try to escape vary, however they are usually due to wanting to cause mischief or wanting to live in the Living Realm. Some continents in the Monster Realm allow for travel between Realms, while others ban it.
When a Monster dies their soul is sent to the gates of the Heaven Realm to be judged by the Angel Petr to see if their soul was good enough to enter the Heaven Realm. If the Monster's soul is deemed unworthy they are sent down to the Hell Realm to be punished for their sins.