Celestial Realm

The Celestial Realm is the homeland of the Goddess Clan.

History
According to the Lady of the Lake, the Celestial Realm was created along with the Goddess Clan by the Supreme Deity, after she was given birth by Chaos.

Not much is known of the Celestial Realm, except that it was essentially composed of "Sky Palaces" built on floating islands, themselves suspended in the clouds. These "Sky Palaces" can be connected to the rest of Britannia by portals generally located in the altars of the Druids, or the Light of Grace.

The Seven Deadly Sins: Cursed by Light
After the end of the Holy War, Mael returned to the Celestial Realm, promising his fellow Archangels to protect it until they revive. There, several Goddesses appear having recovered their physical forms and vow to follow Mael in his new mission.

Trivia

 * The Celestial Realm is likely based off the concept of Heaven from monotheistic religions and others such as the Elysium Fields from ancient Greek mythology.