I'll lay out the basic story. Robin is captured along with an all female crew, and they are killed at a rate of 2-3 per day. Robin is often made to kill the girls herself against her will with mind control. The girls are usually eaten afterwords. One girl is especially well liked, which the captain knows having seen all of the memories of the female crew's captain. She has her frontal lobe forcibly erased, and is set back loose amongst the prisoners, the eventually made to beg to be skullfucked in front of them, then her real personality put back in there right before she dies. Robin is forced to either watch, or do all sorts of things, to 30 girls in all, plus the captain. The whole point being, the captain copies the brain of each girl by touch, and wants to make Robin suffer so he can "save the best for last", aka take what he really wants, Robins Poneglyph knowledge. This happens 11 years prior to the events of Post Ennies Lobby. In the present, Nami is unexpectedly killed. Robin is taken later and forced to destroy her own living brain, then use it on the man as a cocksleeve.