Nagato summons a giant statue that releases multiple chakra rods from its abdomen that pierce Nagato’s back. When the rods are in place, Nagato uses the statue to spew a dragon-like creature from its mouth, which removes the souls of any person it comes in contact with. After serving its purpose, the chakra rods break off and remain embedded in Nagato’s back while the statue disappears. The technique seems to take a considerable toll on Nagato, who becomes more and more emaciated for the duration of the technique. This began the moment the chakra rods penetrated his body
Source: Narutowiki
