In the original story, Orochimaru had mastered Ryūchi Cave's Cursed Seal Technique.
The power of the cursed seal came from Jugo's innate sage-transformation physique. Jugo could unconsciously absorb natural energy and enter a weakened version of Sage Mode.
By extracting Jugo's somatic cells and bodily fluids, then combining them with his own research, Orochimaru developed a transplantable "Cursed Seal Technique" that allowed others to gain power boosts similar to Sage Mode.
Senjutsu was powerful, but its side effects were equally troublesome. While increasing chakra, strength, and speed, it also caused physical mutations, leading to rampages, loss of control, and even death.
It seemed Orochimaru's research had not come from nowhere. Before him, Tobirama Senju had already conducted similar experiments.
Katsuyu said, "All three great sage regions possess senjutsu inheritances, but for many years, none of them have seen a ninja capable of unlocking Sage Mode.
Sage Mode is extremely difficult.
If one makes a mistake while training in Mount Myoboku's Sage Mode, they will petrify and become a stone toad.
If one makes a mistake while training in Ryūchi Cave's Sage Mode, they will be eaten by giant snakes.
If one makes a mistake while training in Shikkotsu Forest's Sage Mode, their muscles will dissolve, their fat will dissolve, and their internal organs will dissolve.
Just like my body, beneath the skin, it turns into bodily fluid."
Hearing Katsuyu's description, even Seiei Senju, who was extremely reckless, began to hesitate.
Kawadera Uchiha was different. He knew Orochimaru had already found a way through this path. There was hope on this path.
He said, "I read in Lord Kagami's notes that Lord Tobirama said this path would definitely succeed, and that cursed seals could raise people of ordinary aptitude to the level of Jonin."
Within the Sea of Consciousness, Tobirama Senju