Shadow Realm

Containment orbs can hold any living entity. Players are living entities. What, then, happens when you put a player in a containment orb? They're sent to the Shadow Realm, of course. This is a special realm whose ID is -1. There's a little circle in the center where captured players are sent and a puppet sort of dude just sitting there. Outside of that little region is an infinite maze that stretches on forever.

Gangblanc chilling in the Shadow Realm.