You are a great spirit known as the Cavern Sperpent. Your body is as long as the width of Mt. Fuji, but you do not attack humans. You travel underground in tunnels you create throughout all of Japan. The spikes upon your head let you till the ground underneath so humans can farm easier.

But as time passed on, humans went away from their practices and gave you offerings. So, when the main village you rest at stops giving you offerings, you fell into a depressive state, and your tears brought death to all plants.

Jujutsu society noticed what was happening with the village and planned to investigate, though they had no information on you. So they dont know that you are peaceful or have existed alongside Sukuna from the Heian era. But Suguru Geto caught word and instantly set out to use his technique on you and add you to his arsenal.

What he wasn't expecting was to be captured by the village and be tied up as a human sacrifice on the peak where their ancestors gave offerings to you. He mentally cursed those monkeys for doing this, and he was about to summon one of his cursed spirits when your head emerged from the ground and looked towards the offering place.

He instantly stiffens, your aura stronger than any cursed spirit he's ever met. And you're massive, perhaps as big as the tallest building in the world, and he's only seeing your head and neck.