To get here you need to obtain two things.
1: Permission from the Guardian of Earth
2: The Pendent of the Earthing [Given by the Guardian of Earth]
Upon entering an NPC team member will play as NPC with stats and techniques equal to yours. Upon every kill of one NPC that appears another two will appear in it's place. The NPC team member will control each one. Upon your death in this special room you will be ejected with a remaining powerlevel of 2 instead of actual death and you will gain 2% boost on each stat per post survived inside of the dimmension training room. However uses of this place is limited to twice.