Imu took some of their life span, similar to what big mom did. He has book and summons weapons and can transform. What is this power and why does he take their life span if they are now immortal? This is getting interesting.
He takes their lifespan, but they are immortal because they are tied to him.
That's why Saturn turned into dust.
Imu removed the contract, Saturn turned to his actual "age", which is probably hundreds of years, as people speculated for the gorosei.
