Lake Salisbury

is a lake, known for having the highest concentration of magic power in all of Britannia.

Background
A legend says that a princess who lives in the lake bestowed a mysterious sword to a human king. This legend actually refer to the Lady of the Lake, who gave the sword Excalibur to Carfen, a master swordsman.

Demon King arc
After take possession of Zeldris's body, the Demon King goes to the magic lake of Salisbury in order to recover the magic that he lost in his fight with the Seven Deadly Sins. There, he waits for Meliodas who arrive in company of Elizabeth. A fight is then unleashed between them, with the other six Sins joining eventually. During the fight, the Demon King gain access to an unlimited magic source provided by the lake. Thus, Diane uses her Mother Creation to destroy the surrounding terrain and force the Demon King out of the lake, destroying most of it in the process.

All the water of the lake maintained acumulated at the end of the a pit. When Meliodas destroy the Demon King with a combined attack from all the Sins, Merlin instructs Meliodas in direct the attack to the lake in order for it to absorb all the excess of power from their attack and prevent it from destroying Britannia.

Current arc
When Merlin decides to reveal her true goal, she teleports the Sins and Elizabeth to Lake Salisbury where they find Hawk and Hawk Mama in front of the orb of water that used to be the lake. Merlin then says it is time to start, when Meliodas asks her what, Merlin surprises everyone by declaring that she refers to Arthur's awakening.

Upon putting herself over the lake, Merlin removes Arthur's body still pierced by Excalibur from the Boar Hat. She says that all the preparations are set and asks the "princess" if she is ready, to which a voice from the lake asks if it is finally time to meet their master. As the lake water begins to shine and its light reaches Excalibur, Merlin tells Arthur that she was wrong since the sword was not the one that would kill him but the key to advancing to his new stage. Merlin uses the "key" to unlock the door.

After an explosion of light, Arthur wakes up having revived as the "King of Chaos".

Fights and Events

 * Seven Deadly Sins & Elizabeth Liones vs. Demon King

Trivia

 * The legend mentioned in the story is a reference to Lady of the Lake from the Arthurian Legends. This character is the one who gives Arthur his iconic sword, Excalibur.