the planets in the solar system are all different ages. the rock planet is so old that life has gone extinct and been recreated three separate times. because of this, passbies like Pi Roko preach that death and extinction are not so important, even though every life is special. in the middle of my story that will never happen, the rock planet experiences a fourth extinction after Pi Roko is murdered by her disciple, forcing what few survivors remain to migrate to the water and already-crippled air planet.