Phoenix Space

The Phoenix Space is a spiritual space where those wearing costumes can visit. If one's willpower is strong enough they can force themselves out of the Phoenix Space, as shown by Child Emperor. The same can be said for breaking into phoenix space, as shown by Saitama.

Appearance
The Phoenix Space is a calm and relaxed open plain with multiple statues of characters from the kid's TV show "Animal Kingdom" scattered throughout it, as the space itself is a reflection of Phoenix Man's psyche.

Monster Association Arc
While Phoenix Man was fighting Child Emperor, Phoenix Man transported himself and Child Emperor to the Phoenix Space to try and recruit Child Emperor into becoming his ally so they could destroy all Humans and Monsters and rule the world. To Phoenix Man's disbelief, Child Emperor refuses and escapes with his own sheer willpower. While continuing their battle, Phoenix Man teleports himself and Child Emperor once again into the Phoenix Space, where he continues to try to persuade Child Emperor into becoming his ally, but is interrupted by Saitama, who found a way to break into the spiritual space by "knocking until it opened". Outsiders who are not in this space hear conversations within it as whispers.