Jack led the group to the entrance of the time chamber. Only core members were allowed access to the time chamber, so the existence of the two little nightmares won't be exposed to too many people.
Additionally, this time chamber let Sol and Fira experience ten times the time outside. Peniel ensured Jack that although the time chamber didn't affect the player's age system, real-life aging was still affected by the chamber. This meant that the little nightmares would grow at a pace ten times than they would have normally outside.
The time chamber also had dense mana due to the installed mana-gathering stone. This dense mana gave any native a good growing environment.
Pandora followed them. She didn't allow herself to get unsummoned until she was sure her sister's two offspring were properly settled.