3,000 years ago
The Heaven's Theater was place built by the Goddess Clan, and at some point it was destroyed and abandoned.
During their clans' brief peace, Elizabeth and Meliodas met secretly on the abandoned remains of Heaven's Theater, telling their wishes and lifes with family, with the Archangel Mael being the only one who knew it.
When Estarossa takes Elizabeth from the battlefield, both fall in the middle of the Heaven's Theater. Estarossa says that she decided to take her there because it was the place she and Meliodas knew well.
When Estarossa absorbs Elizabeth in his darkness, King, Sariel, Tarmiel and Derieri arrive with the intention of saving her. While fighting a warped Estarossa, the memories altered by the forbidden spell of the magician Gowther 3,000 years ago begin to return to normality, revealing to everyone's surprise that "Estarossa" is actually Mael.
Gowther and Hawk also arrive at the Theater, and Gowther reveals he is responsible for what happened to Mael, asking to be destroyed as punishment. However, King decides to face a Mael possessed by the power of the Commandments and Sariel, Tarmiel and Derieri join him.
However, when the fight seemed won, Mael manages to kill Derieri and absorb her Commandment, obtaining an incalculable power in exchange for his rationality, ending up killing Sariel and Tarmiel in the middle of his transformation.
Although Diane and Oslo join the battle, Mael's power proves to be too much for all of them together, with Oslo eventually sacrificing his life to save them all from one of his attacks. There, Diane is forced to use Gideon's special power, Lightning Rod, to redirect Mael's attacks to the earth. After redirecting two of his Jiai no Kougyoku, the Heaven's Theater ends up being completely destroyed as it could not stand the damage.