Okay so as we all know that the current Geto suguru is not the real one as he is deceased and the one that is now inhabited his body is a +1000 year old sorcerer named Kenjaku.
Kenjaku can incarnate into other people's body. He is also knowledgeable when it comes to the jujutsu world and curses as he's been around for a long time. So far as we know the bodies kenjaku has incarnated into is Itadori's mother,Noritoshi Kamo and now the current Geto suguru.
FANART BY: Aki-yehuo(Art Station)
But right now where going to talk about Noritoshi Kamo and what Kenjaku did while he incarnated his body. Noritoshi Kamo is currently known in the Jujutsu world as the most evil and vile sorcerer there is, he also is the one who put a stain on the Kamo clans reputation as we know this clan is one of the big 3 clans.
The reason why Noritoshi is known as evil and vile is because back in the beginning of the Meiji Era, a woman with a special genetic bore a hybrid child that was half-human and half-curse. It was a pregnancy that was so abnormal and unnatural that caused her to be shunned by her family. She fled with her child in her hands to a temple that was ran by Jujutsu sorcerers, hoping that they would help her in anyway. However, Noritoshi Kamo who was one of the sorcerers who ran the temple at that time forced them to become his prisoners out of his intellectual curiosity. The woman had nine pregnancies and nine abortions, there is little about this and the woman, as all the records surrounding them is either sealed away somewhere or destroyed. But the nine aborted fetuses that the woman had were experimented by Noritoshi Kamo that are now known as Cursed Womb: Death Paintings.
At some point in life Tokyo Jujutsu high were able to obtain three Death Paintings Wombs. They used a constraint to seal them and hid them within a storage house that was protected by Tengens barrier but later on the three Death Paintings would be stolen by Mahito. The three death Paintings that Mahito stole are now known as Choso, Eso, and Kechizu. So far these three are the only known death Paintings.....well for now at least.