Spell of Immortality

Spell of Immortality (불사의 주술, bulsaui jusul) is an incredibly powerful spell that was used by Grand De Jah and Grand De Sah, which were perfected with the help of Po Bidau Gustang to create a place called the "Spirit Room" where they stored the souls of 43rd Floor citizens and created a way for people who live on that floor to live forever without aging. Side effect of the spell is that the people under this spell cannot leave the floor. They must stay there forever and in return they will be granted immortlity.

Red Thryssa can nullify the immortality spell cast on the 43rd Floor. Baam managed to surpass this spell using Shinwonryu. Hoaqin managed to envelop the spell with his own in order to steal all the souls trapped in the Spirit Room and regain his powers. He managed to do so, but he could not overcome the curse of being unable to leave the floor, allowing Gustang to effortlessly remove the souls from White and return it without even having to stop him from trying to escape, as no matter how hard White tried, he was not able to oppose the curse placed on the souls.

Trivia

 * Despite being the one who helped De Sah and De Jah complete the spell, Gustang, one of the 10 Family Heads, who were said to have the power to break even a powerful spell placed on the bases of the 10 Families, admits even if he wanted to, he couldn't remove the spell as it isn't easy for him to even remove other completed spells, indicating the immortality spell is far more powerful than most other spells.