Ouroboros (世界喰らいの蛇(ウロボロス) Sekai kurai no hebi(Uroborosu)?) is a level Thirteen Dark Art, making it one of the forbidden spells. It is one of the origins of Moroha. It is a spell that summons a magical sea that devours everything hostile to user, with the user being able to manipulate the water freely. The sea will not go away even after the spell is used. It's even been said that the entire area has changed and the maps had to be altered. Moroha used it against Vasilisa Yuryevna Mostovaya, the Lightning Emperor, in Volume 5 of the light novel and Episode 10 of the anime.
The Verses are as follows:
"It all began in water."
"It all returns to the water."
"In other words, water is life, and yet death."
"The mother that bears us, and a devouring serpent."
"All things are in flux, and not even time can go against the current."
"Like a boat tossed about on a great river, in the end it too is merely devoured."
"Ahh, cruel uncertain providence."
"But that cruelty and uncertainty have already forgotten."
"The face of their most beloved mother. "
"I will become a serpent, open my mouth, and devour billions of lands."
"An eternal void, never filling.''
''An eternal pleasure, never satiated.''
''You must change, all things, and return to my maw.''